@article{divilov_eckert_toher_friedrich_zettel_brenner_fahrenholtz_wolfe_zurek_maria_et al._2024, title={A priori procedure to establish spinodal decomposition in alloys}, volume={266}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2024.119667}, abstractNote={Spinodal decomposition can improve a number of essential properties in materials, especially hardness. Yet, the theoretical prediction of the onset of this phenomenon (e.g., temperature) and its microstructure (e.g., wavelength) often requires input parameters coming from costly and time-consuming experimental efforts, hindering rational materials optimization. Here, we present a procedure where such parameters are not derived from experiments. First, we calculate the spinodal temperature by modeling nucleation in the solid solution while approaching the spinode boundary. Then, we compute the spinodal wavelength self-consistently using a few reasonable approximations. Our results show remarkable agreement with experiments and, for NiRh, the calculated yield strength due to spinodal microstructures surpasses even those of Ni-based superalloys. We believe that this procedure will accelerate the exploration of the complex materials experiencing spinodal decomposition, critical for their macroscopic properties.}, journal={ACTA MATERIALIA}, author={Divilov, Simon and Eckert, Hagen and Toher, Cormac and Friedrich, Rico and Zettel, Adam C. and Brenner, Donald W. and Fahrenholtz, William G. and Wolfe, Douglas E. and Zurek, Eva and Maria, Jon-Paul and et al.}, year={2024}, month={Mar} }
 @article{filipovic_obradovic_hilmas_fahrenholtz_brenner_maria_wolfe_zurek_campilongo_curtarolo_2024, title={A super-hard high entropy boride containing Hf, Mo, Ti, V, and W}, ISSN={["1551-2916"]}, DOI={10.1111/jace.19795}, abstractNote={Abstract}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Filipovic, Suzana and Obradovic, Nina and Hilmas, Greg E. and Fahrenholtz, William G. and Brenner, Donald W. and Maria, Jon-Paul and Wolfe, Douglas E. and Zurek, Eva and Campilongo, Xiomara and Curtarolo, Stefano}, year={2024}, month={Mar} }
 @article{divilov_eckert_hicks_oses_toher_friedrich_esters_mehl_zettel_lederer_et al._2024, title={Disordered enthalpy-entropy descriptor for high-entropy ceramics discovery}, volume={625}, ISSN={["1476-4687"]}, DOI={10.1038/s41586-023-06786-y}, abstractNote={The need for improved functionalities in extreme environments is fuelling interest in high-entropy ceramics1-3. Except for the computational discovery of high-entropy carbides, performed with the entropy-forming-ability descriptor4, most innovation has been slowly driven by experimental means1-3. Hence, advancement in the field needs more theoretical contributions. Here we introduce disordered enthalpy-entropy descriptor (DEED), a descriptor that captures the balance between entropy gains and enthalpy costs, allowing the correct classification of functional synthesizability of multicomponent ceramics, regardless of chemistry and structure. To make our calculations possible, we have developed a convolutional algorithm that drastically reduces computational resources. Moreover, DEED guides the experimental discovery of new single-phase high-entropy carbonitrides and borides. This work, integrated into the AFLOW computational ecosystem, provides an array of potential new candidates, ripe for experimental discoveries.}, number={7993}, journal={NATURE}, author={Divilov, Simon and Eckert, Hagen and Hicks, David and Oses, Corey and Toher, Cormac and Friedrich, Rico and Esters, Marco and Mehl, Michael J. and Zettel, Adam C. and Lederer, Yoav and et al.}, year={2024}, month={Jan} }
 @article{toher_oses_esters_hicks_kotsonis_rost_brenner_maria_curtarolo_2022, title={High-entropy ceramics: Propelling applications through disorder}, ISSN={["1938-1425"]}, DOI={10.1557/s43577-022-00281-x}, abstractNote={Disorder enhances desired properties, as well as creating new avenues for synthesizing materials. For instance, hardness and yield stress are improved by solid-solution strengthening, a result of distortions and atomic-size mismatches. Thermochemical stability is increased by the preference of chemically disordered mixtures for high-symmetry superlattices. Vibrational thermal conductivity is decreased by force-constant disorder without sacrificing mechanical strength and stiffness. Thus, high-entropy ceramics propel a wide range of applications: from wear-resistant coatings and thermal and environmental barriers to catalysts, batteries, thermoelectrics, and nuclear energy management. Here, we discuss recent progress of the field, with a particular emphasis on disorder-enhanced properties and applications. Graphical abstract}, journal={MRS BULLETIN}, author={Toher, Cormac and Oses, Corey and Esters, Marco and Hicks, David and Kotsonis, George N. and Rost, Christina M. and Brenner, Donald W. and Maria, Jon-Paul and Curtarolo, Stefano}, year={2022}, month={Apr} }
 @article{jaszewski_hoglund_costine_weber_fields_sales_vaidya_bellcase_loughlin_salanova_et al._2022, title={Impact of oxygen content on phase constitution and ferroelectric behavior of hafnium oxide thin films deposited by reactive high-power impulse magnetron sputtering}, volume={239}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2022.118220}, journal={ACTA MATERIALIA}, author={Jaszewski, Samantha T. and Hoglund, Eric R. and Costine, Anna and Weber, Marc H. and Fields, Shelby S. and Sales, Maria Gabriela and Vaidya, Jaykumar and Bellcase, Leah and Loughlin, Katie and Salanova, Alejandro and et al.}, year={2022}, month={Oct} }
 @article{hossain_borman_oses_esters_toher_feng_kumar_fahrenholtz_curtarolo_brenner_et al._2021, title={Entropy Landscaping of High-Entropy Carbides}, ISSN={["1521-4095"]}, DOI={10.1002/adma.202102904}, abstractNote={Abstract}, journal={ADVANCED MATERIALS}, author={Hossain, Mohammad Delower and Borman, Trent and Oses, Corey and Esters, Marco and Toher, Cormac and Feng, Lun and Kumar, Abinash and Fahrenholtz, William G. and Curtarolo, Stefano and Brenner, Donald and et al.}, year={2021}, month={Sep} }
 @article{tomko_runnerstrom_wang_chu_nolen_olson_kelley_cleri_nordlander_caldwell_et al._2021, title={Long-lived modulation of plasmonic absorption by ballistic thermal injection}, volume={16}, ISSN={["1748-3395"]}, DOI={10.1038/s41565-020-00794-z}, abstractNote={Light–matter interactions that induce charge and energy transfer across interfaces form the foundation for photocatalysis1,2, energy harvesting3 and photodetection4, among other technologies. One of the most common mechanisms associated with these processes relies on carrier injection. However, the exact role of the energy transport associated with this hot-electron injection remains unclear. Plasmon-assisted photocatalytic efficiencies can improve when intermediate insulation layers are used to inhibit the charge transfer5,6 or when off-resonance excitations are employed7, which suggests that additional energy transport and thermal effects could play an explicit role even if the charge transfer is inhibited8. This provides an additional interfacial mechanism for the catalytic and plasmonic enhancement at interfaces that moves beyond the traditionally assumed physical charge injection9–12. In this work, we report on a series of ultrafast plasmonic measurements that provide a direct measure of electronic distributions, both spatially and temporally, after the optical excitation of a metal/semiconductor heterostructure. We explicitly demonstrate that in cases of strong non-equilibrium, a novel energy transduction mechanism arises at the metal/semiconductor interface. We find that hot electrons in the metal contact transfer their energy to pre-existing free electrons in the semiconductor, without an equivalent spatiotemporal transfer of charge. Further, we demonstrate that this ballistic thermal injection mechanism can be utilized as a unique means to modulate plasmonic interactions. These experimental results are well-supported by both rigorous multilayer optical modelling and first-principle ab initio calculations. An energy transduction mechanism across metal/semiconductor interfaces, which relies on electron–electron energy transfer rather than the transport of charge, is demonstrated through ultrafast infrared spectroscopy. This ballistic thermal injection process allows for extended modulation of plasmonic absorption in epsilon-near-zero media.}, number={1}, journal={NATURE NANOTECHNOLOGY}, author={Tomko, John A. and Runnerstrom, Evan L. and Wang, Yi-Siang and Chu, Weibin and Nolen, Joshua R. and Olson, David H. and Kelley, Kyle P. and Cleri, Angela and Nordlander, Josh and Caldwell, Joshua D. and et al.}, year={2021}, month={Jan}, pages={47–51} }
 @article{esters_oses_hicks_mehl_jahnatek_hossain_maria_brenner_toher_curtarolo_2021, title={Settling the matter of the role of vibrations in the stability of high-entropy carbides}, volume={12}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-021-25979-5}, abstractNote={Abstract}, number={1}, journal={NATURE COMMUNICATIONS}, author={Esters, Marco and Oses, Corey and Hicks, David and Mehl, Michael J. and Jahnatek, Michal and Hossain, Mohammad Delower and Maria, Jon-Paul and Brenner, Donald W. and Toher, Cormac and Curtarolo, Stefano}, year={2021}, month={Sep} }
 @article{grady_seo_tsuji_ndayishimiye_lowum_dursun_maria_randall_2020, title={Cold Sintering for High-Temperature Electrochemical Applications}, volume={29}, ISSN={["1944-8783"]}, DOI={10.1149/2.F08204IF}, abstractNote={Although cold sintering remains an emerging processing technique, it is noteworthy to consider recent progress in materials that are of interest to electrochemical systems with elevated service temperatures. Here we discuss a broad number of materials ranging from alkali electrolytes for solid state batteries, to oxygen ion conductors for gas sensing. We also discuss the opportunity to co-fire mixed ionic conductors into multilayered devices. Given the low-temperature sintering temperatures with the cold sintering process (CSP), we will discuss some insights into operating ceramics at temperatures near or above their processing temperature.}, number={4}, journal={ELECTROCHEMICAL SOCIETY INTERFACE}, author={Grady, Zane and Seo, Joo-Hwan and Tsuji, Kosuke and Ndayishimiye, Arnaud and Lowum, Sarah and Dursun, Sinan and Maria, Jon-Paul and Randall, Clive A.}, year={2020}, month={Dec} }
 @article{sachet_aspnes_maria_franzen_2020, title={Critical Test of the Interaction of Surface Plasmon Resonances with Molecular Vibrational Transitions}, volume={124}, ISSN={["1520-5215"]}, DOI={10.1021/acs.jpca.9b10835}, abstractNote={We determine the absorption spectra of a gas due to evanescent plasmonic electromagnetic fields in a system where surface interactions (physisorption and chemisorption) are demonstrably negligible. The plasmonic host material, degenerate semiconductor CdO:Dy, has high mobility (366 - 450 cm2/Vs) and carrier density (0.6 - 3.5 x 1020 cm-3) and therefore supports low-loss surface plasmon resonances in the mid-IR. This high mobility layer gives the highest resolution observed in a plasmonic conducting layer in the infrared, higher than gold and rivaling silver at optical frequencies in the resolution of spectral features relative to the plasmon energy. This high resolution permits new understanding of the nature of the interaction of emerging fields with molecular transitions. Using different carrier concentrations, the resonance condition of the surface plasmon polariton (SPP) frequency (ω_SPP) and N2O vibrational absorption spectral frequency (ω_(N_2 O)) can be controlled, thereby allowing a critical test of field-molecule interactions. Experiment and theory both indicate a dispersive N2O line shape for ω_SPPω_(N_2 O) and an abrupt change between the two when the resonance condition ω_SPP=ω_(N_2 O) is reached. A first-order expansion of the Airy equation describes this behavior analytically. The SPP surface enhancement is 6.8±0.5 on resonance, less than enhancements observed in other systems, but in agreement with recent quantitative reports of surface enhanced infrared reflection absorption spectroscopy (SEIRA). Our results show that interactions of infrared SPPs with molecular vibrations are in the weak coupling limit, and that enhancements comparable those reported for noble metals are achievable.}, number={9}, journal={JOURNAL OF PHYSICAL CHEMISTRY A}, author={Sachet, Edward and Aspnes, D. E. and Maria, J-P and Franzen, Stefan}, year={2020}, month={Mar}, pages={1744–1753} }
 @article{rost_borman_hossain_lim_quiambao-tomko_tomko_brenner_maria_hopkins_2020, title={Electron and phonon thermal conductivity in high entropy carbides with variable carbon content}, volume={196}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2020.06.005}, abstractNote={Due to their diverse bonding character and corresponding property repertoire, carbides are an important class of materials regularly used in modern technologies, including aerospace applications and extreme environments, catalysis, fuel cells, power electronics, and solar cells. The recent push for novel materials has increased interest in high entropy carbides (HECs) for such applications. The extreme level of tunability alone makes HECs a significant materials platform for a variety of fundamental studies and functional applications. We investigate the thermal conductivity of high entropy carbide thin films as carbon stoichiometry is varied. The thermal conductivity of the HEC decreases with an increase in carbon stoichiometry, while the respective phonon contribution scales with elastic modulus as the excess carbon content increases. Based on the carbon content, the HECs transition from an electrically conducting metal-like material with primarily metallic bonding to a primarily covalently-bonded crystal with thermal conductivities largely dominated by the phononic sub-system. When the carbon stoichiometry is increased above this critical transition threshold dictating bonding character, the electronic contribution to thermal conductivity is minimized, and a combination of changes in microstructure, defect concentration and secondary phase formation, and stiffness influence the phononic contribution to thermal conductivity. Our results demonstrate the ability to tune the thermal functionality of high entropy materials through stoichiometries that dictate the type of bonding environment.}, journal={ACTA MATERIALIA}, author={Rost, Christina M. and Borman, Trent and Hossain, Mohammad Delower and Lim, Mina and Quiambao-Tomko, Kathleen F. and Tomko, John A. and Brenner, Donald W. and Maria, Jon-Paul and Hopkins, Patrick E.}, year={2020}, month={Sep}, pages={231–239} }
 @article{matveev_dlott_hanusova_maria_nye_parsons_2020, title={Shock Initiation of Reactive Nanolaminates}, volume={2272}, ISSN={["0094-243X"]}, DOI={10.1063/12.0000877}, abstractNote={The production of heat by reactive nanomaterials occurs at a fuel/oxidizer interface. In order to understand how such materials can be initiated by shock, we studied a model system consisting of a reactive nanolaminate (RNL) with a well-defined planar interface. In addition, an organic thin layer could be intercalated between the fuel and oxidizer to modulate the reaction. We studied a stoichiometric mixture of Zr fuel and CuO oxidizer and the modulator layer was polyurea produced by molecular layer deposition. The RNL was shocked using 0.5 mm diameter Al flyer plates launched by a pulsed laser at 1.5 km/s. We found that little or no reaction was produced immediately under the flyer plate where the interface experiences compression only. Instead the reaction was efficiently initiated by shear waves propagating out from the edges of the flyer plate. The RNL reaction temperature during shock was 4000K, and after the shock dissipated, the RNL reacted at 3000K. Modulator layers caused the reaction to slow down with the effect increasing with increasing modulator thickness up to 500 nm.}, journal={SHOCK COMPRESSION OF CONDENSED MATTER - 2019}, author={Matveev, Sergey M. and Dlott, Dana D. and Hanusova, Petra and Maria, Jon-Paul and Nye, Rachel and Parsons, Gregory}, year={2020} }
 @article{nolen_runnerstrom_kelley_luk_folland_cleri_maria_caldwell_2020, title={Ultraviolet to far-infrared dielectric function of n-doped cadmium oxide thin films}, volume={4}, ISSN={["2475-9953"]}, DOI={10.1103/PhysRevMaterials.4.025202}, abstractNote={Spectroscopic ellipsometry and Fourier transform infrared spectroscopy were applied to extract the ultraviolet to far-infrared (150 – 33,333 cm) complex dielectric functions of high-quality, sputtered Indium-doped Cadmium Oxide (In:CdO) thin, crystalline films on MgO substrates possessing carrier densities ( ) ranging from 1.1 10 cm to 4.1 10 cm. A multiple oscillator fit model was used to identify and analyze the three major contributors to the dielectric function and their dependence on doping density: interband transitions in the visible, free-carrier excitations (Drude response) in the nearto far-infrared, and IR-active optic phonons in the far-infrared. More specifically, values pertinent to the complex dielectric function such as the optical bandgap ( ), are shown here to be dependent upon carrier density, increasing from approximately 2.5 to 3 eV, while the high-frequency permittivity ( ) decreases from 5.6 to 5.1 with increasing carrier density. The plasma frequency ( ) scales as , resulting in values occurring within the midto near-IR, and the effective mass ( ) was also observed to exhibit doping density dependent changes, reaching a minimum of 0.11 in unintentionally doped films (1.1 10 ). Good quantitative agreement with prior work on polycrystalline, higher doped CdO films is also demonstrated, illustrating the generality of the results. The analysis presented here will aid in predictive calculations for CdO-based next-generation nanophotonic and optoelectronic devices, while also providing an underlying physical description of the key properties dictating the dielectric response in this atypical semiconductor system.}, number={2}, journal={PHYSICAL REVIEW MATERIALS}, author={Nolen, J. Ryan and Runnerstrom, Evan L. and Kelley, Kyle P. and Luk, Ting S. and Folland, Thomas G. and Cleri, Angela and Maria, Jon-Paul and Caldwell, Joshua D.}, year={2020}, month={Feb} }
 @article{radue_runnerstrom_kelley_rost_donovan_grimley_lebeau_maria_hopkins_2019, title={Charge confinement and thermal transport processes in modulation-doped epitaxial crystals lacking lattice interfaces}, volume={3}, ISSN={["2475-9953"]}, DOI={10.1103/PhysRevMaterials.3.032201}, abstractNote={Elizabeth Radue,1 Evan L. Runnerstrom,2,3 Kyle P. Kelley,2,3 Christina M. Rost,1 Brian F. Donovan,4 Everett D. Grimley,2 James M. LeBeau,2 Jon-Paul Maria,2,3 and Patrick E. Hopkins1,5,6,* 1Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia 22904, USA 2Department of Materials Science, North Carolina State University, Raleigh, North Carolina 27695, USA 3Department of Materials Science and Engineering, Pennsylvania State University, State College, Pennsylvania 16801, USA 4Department of Physics, United States Naval Academy, Annapolis, Maryland 21402, USA 5Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904, USA 6Department of Physics, University of Virginia, Charlottesville, Virginia 22904, USA}, number={3}, journal={PHYSICAL REVIEW MATERIALS}, author={Radue, Elizabeth and Runnerstrom, Evan L. and Kelley, Kyle P. and Rost, Christina M. and Donovan, Brian F. and Grimley, Everett D. and LeBeau, James M. and Maria, Jon-Paul and Hopkins, Patrick E.}, year={2019}, month={Mar} }
 @article{kang_floyd_lowum_long_dickey_maria_2019, title={Cold sintering with dimethyl sulfoxide solutions for metal oxides}, volume={54}, ISSN={0022-2461 1573-4803}, url={http://dx.doi.org/10.1007/s10853-019-03410-1}, DOI={10.1007/s10853-019-03410-1}, number={10}, journal={Journal of Materials Science}, publisher={Springer Science and Business Media LLC}, author={Kang, Xiaoyu and Floyd, Richard and Lowum, Sarah and Long, Daniel and Dickey, Elizabeth and Maria, Jon-Paul}, year={2019}, month={Feb}, pages={7438–7446} }
 @article{gaskins_kotsonis_giri_ju_rohskopf_wang_bai_sachet_shelton_liu_et al._2019, title={Corrrection to Thermal Boundary Conductance Across Heteroepitaxial ZnO/GaN Interfaces: Assessment of the Phonon Gas Model}, volume={19}, ISSN={1530-6984 1530-6992}, url={http://dx.doi.org/10.1021/ACS.NANOLETT.9B00022}, DOI={10.1021/ACS.NANOLETT.9B00022}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrrection to Thermal Boundary Conductance Across Heteroepitaxial ZnO/GaN Interfaces: Assessment of the Phonon Gas ModelJohn T. GaskinsJohn T. GaskinsMore by John T. Gaskinshttp://orcid.org/0000-0001-8622-5902, George KotsonisGeorge KotsonisMore by George Kotsonis, Ashutosh GiriAshutosh GiriMore by Ashutosh Girihttp://orcid.org/0000-0002-8899-4964, Shenghong JuShenghong JuMore by Shenghong Juhttp://orcid.org/0000-0001-7863-6947, Andrew RohskopfAndrew RohskopfMore by Andrew Rohskopf, Yekan WangYekan WangMore by Yekan Wang, Tingyu BaiTingyu BaiMore by Tingyu Bai, Edward SachetEdward SachetMore by Edward Sachet, Christopher T. SheltonChristopher T. SheltonMore by Christopher T. Shelton, Zeyu LiuZeyu LiuMore by Zeyu Liu, Zhe ChengZhe ChengMore by Zhe Chenghttp://orcid.org/0000-0001-7827-2979, Brian M. FoleyBrian M. FoleyMore by Brian M. Foley, Samuel GrahamSamuel GrahamMore by Samuel Grahamhttp://orcid.org/0000-0002-1299-1636, Tengfei LuoTengfei LuoMore by Tengfei Luohttp://orcid.org/0000-0003-3940-8786, Asegun HenryAsegun HenryMore by Asegun Henry, Mark S. GoorskyMark S. GoorskyMore by Mark S. Goorsky, Junichiro ShiomiJunichiro ShiomiMore by Junichiro Shiomihttp://orcid.org/0000-0002-3552-4555, Jon-Paul MariaJon-Paul MariaMore by Jon-Paul Maria, and Patrick E. Hopkins*Patrick E. HopkinsMore by Patrick E. Hopkinshttp://orcid.org/0000-0002-3403-743XCite this: Nano Lett. 2019, 19, 2, 1408Publication Date (Web):January 23, 2019Publication History Published online23 January 2019Published inissue 13 February 2019https://pubs.acs.org/doi/10.1021/acs.nanolett.9b00022https://doi.org/10.1021/acs.nanolett.9b00022correctionACS PublicationsCopyright © 2019 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views1238Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail PDF (320 KB) Get e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts}, number={2}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={Gaskins, John T. and Kotsonis, George and Giri, Ashutosh and Ju, Shenghong and Rohskopf, Andrew and Wang, Yekan and Bai, Tingyu and Sachet, Edward and Shelton, Christopher T. and Liu, Zeyu and et al.}, year={2019}, month={Jan}, pages={1408–1408} }
 @article{yang_lu_manjavacas_luk_liu_kelley_maria_runnerstrom_sinclair_ghimire_et al._2019, title={High-harmonic generation from an epsilon-near-zero material}, volume={15}, ISSN={["1745-2481"]}, DOI={10.1038/s41567-019-0584-7}, abstractNote={High-harmonic generation (HHG) from a compact, solid-state medium is highly desirable for applications such as coherent attosecond pulse generation and extreme ultra-violet (EUV) spectroscopy, yet the typically weak conversion of pump light to HHG can largely hinder its applications. Here, we use a material operating in its epsilon-near-zero (ENZ) region, where the real part of its permittivity vanishes, to greatly boost the efficiency of the HHG process at the microscopic level. In experiments, we report high-harmonic emission up to the 9th order directly from a low-loss, solid-state ENZ medium: indium-doped cadmium oxide, with an excitation intensity at the GW cm-2 level. Furthermore, the observed HHG signal exhibits a pronounced spectral red-shift as well as linewidth broadening, resulting from the photo-induced electron heating and the consequent time-dependent resonant frequency of the ENZ film. Our results provide a novel nanophotonic platform for strong field physics, reveal new degrees of freedom for spectral and temporal control of HHG, and open up possibilities of compact solid-state attosecond light sources.}, number={10}, journal={NATURE PHYSICS}, author={Yang, Yuanmu and Lu, Jian and Manjavacas, Alejandro and Luk, Ting S. and Liu, Hanzhe and Kelley, Kyle and Maria, Jon-Paul and Runnerstrom, Evan L. and Sinclair, Michael B. and Ghimire, Shambhu and et al.}, year={2019}, month={Oct}, pages={1022-+} }
 @article{lim_rak_braun_rost_kotsonis_hopkins_maria_brenner_2019, title={Influence of mass and charge disorder on the phonon thermal conductivity of entropy stabilized oxides determined by molecular dynamics simulations}, volume={125}, ISSN={["1089-7550"]}, DOI={10.1063/1.5080419}, abstractNote={It is shown using classical molecular dynamics simulations that phonon scattering from disorder in the interatomic forces introduced by charge transfer and not from mass disorder is needed to explain the thermal conductivity reduction experimentally measured that accompanies the addition of a sixth cation to the entropy stabilized oxide J14 [(Mg0.1Co0.1Ni0.1Cu0.1Zn0.1)O0.5]. The simulations were performed on five entropy-stabilized oxides, J14, and J14 plus Sc, Sn, Cr, or Ge in equi-molar cation proportions. Comparing the simulation results to predictions from the Bridgman equation using properties from the simulations suggests that despite phonon scattering from disorder in both atomic forces and mass, the thermal conductivity for these systems is still above an analytical limit for an amorphous structure.}, number={5}, journal={JOURNAL OF APPLIED PHYSICS}, author={Lim, M. and Rak, Zs. and Braun, J. L. and Rost, C. M. and Kotsonis, G. N. and Hopkins, P. E. and Maria, J. -P. and Brenner, D. W.}, year={2019}, month={Feb} }
 @article{floyd_lowum_maria_2019, title={Instrumentation for automated and quantitative low temperature compaction and sintering}, volume={90}, ISSN={["1089-7623"]}, DOI={10.1063/1.5094040}, abstractNote={This report describes the design, operation, and capabilities of a semiautomated uniaxial press with in situ measurement of platen displacements designed to facilitate, understand, and improve compaction and densification of particulate materials contained in conventional metal dies under modest temperatures. While not exclusive to one implementation, the instrumentation is particularly well-suited to study cold sintering. The instrumentation shares similarities to dilatometry, given the ability to monitor pellet compaction, and calorimetry, given the ability to monitor phase transitions by their molar volume signatures. Pursuant to these similarities, we refer to this device as a sinterometer. A critical benefit to this automation is a new ability to conduct experiments unattended for indefinite amounts of time under constant pressure while collecting quantitative data. We demonstrate densification profile computation (i.e., sintegram) using this instrument, including methods to account for the thermal expansion background of the metal die. A set of examples are provided where this stable and long-term data collection allows one to identify densification mechanisms and phase transformations that occur during cold sintering, which would be extremely time consuming, or impossible, to extract using a conventional, manual press.}, number={5}, journal={REVIEW OF SCIENTIFIC INSTRUMENTS}, author={Floyd, Richard and Lowum, Sarah and Maria, Jon-Paul}, year={2019}, month={May} }
 @article{lowum_floyd_bermejo_maria_2019, title={Mechanical strength of cold-sintered zinc oxide under biaxial bending}, volume={54}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-018-3173-8}, number={6}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Lowum, Sarah and Floyd, Richard and Bermejo, Raul and Maria, Jon-Paul}, year={2019}, month={Mar}, pages={4518–4522} }
 @article{kang_floyd_lowum_cabral_dickey_maria_2019, title={Mechanism studies of hydrothermal cold sintering of zinc oxide at near room temperature}, volume={102}, ISSN={0002-7820 1551-2916}, url={http://dx.doi.org/10.1111/JACE.16340}, DOI={10.1111/jace.16340}, abstractNote={Abstract}, number={8}, journal={Journal of the American Ceramic Society}, publisher={Wiley}, author={Kang, Xiaoyu and Floyd, Richard and Lowum, Sarah and Cabral, Matthew and Dickey, Elizabeth and Maria, Jon‐Paul}, year={2019}, month={Feb}, pages={4459–4469} }
 @article{kelley_runnerstrom_sachet_shelton_grimley_klump_lebeau_sitar_suen_padilla_et al._2019, title={Multiple Epsilon-Near-Zero Resonances in Multilayered Cadmium Oxide: Designing Metamaterial-Like Optical Properties in Monolithic Materials}, volume={6}, ISSN={["2330-4022"]}, DOI={10.1021/acsphotonics.9b00367}, abstractNote={In this Letter, we demonstrate a new class of infrared nanophotonic materials based on monolithic, multilayered doped cadmium oxide (CdO) thin films, where each CdO layer is individually tuned to support a separate epsilon-near-zero (ENZ) resonance. Infrared reflectivity measurements reveal that the optical response of the multilayered stack combines multiple discrete absorption events, each associated with an individual ENZ plasmonic polaritonic mode. Structural and chemical characterization confirm that the multilayers are homoepitaxial and monolithic, with internal interfaces defined by discrete steps in dopant density and carrier concentration. Structurally, the layers are indistinguishable as they differ from their neighbors by only ∼1 in 10000 constituent atoms. The optoelectronic property contrast, however, is pronounced, as each layer maintains an independent electron concentration, as corroborated by secondary ion mass spectroscopy and numerical solutions to Poisson’s equation. It is this electro...}, number={5}, journal={ACS PHOTONICS}, author={Kelley, Kyle P. and Runnerstrom, Evan L. and Sachet, Edward and Shelton, Christopher T. and Grimley, Everett D. and Klump, Andrew and LeBeau, James M. and Sitar, Zlatko and Suen, Jonathan Y. and Padilla, Willie J. and et al.}, year={2019}, month={May}, pages={1139–1145} }
 @article{akouala_kumar_punugupati_reynolds_reynolds_mily_maria_narayan_hunte_2019, title={Planar Hall effect and anisotropic magnetoresistance in semiconducting and conducting oxide thin films}, volume={125}, ISSN={0947-8396 1432-0630}, url={http://dx.doi.org/10.1007/S00339-019-2592-Y}, DOI={10.1007/s00339-019-2592-y}, number={5}, journal={Applied Physics A}, publisher={Springer Science and Business Media LLC}, author={Akouala, Christer R. and Kumar, Raj and Punugupati, Sandhyarani and Reynolds, C. Lewis and Reynolds, Judith G. and Mily, Edward J. and Maria, Jon-Paul and Narayan, Jagdish and Hunte, Frank}, year={2019}, month={Apr} }
 @article{runnerstrom_kelley_folland_nolen_engheta_caldwell_maria_2019, title={Polaritonic Hybrid-Epsilon-near-Zero Modes: Beating the Plasmonic Confinement vs Propagation-Length Trade-Off with Doped Cadmium Oxide Bilayers}, volume={19}, ISSN={["1530-6992"]}, DOI={10.1021/acs.nanolett.8b04182}, abstractNote={Polaritonic materials that support epsilon-near-zero (ENZ) modes offer the opportunity to design light-matter interactions at the nanoscale through extreme subwavelength light confinement, producing phenomena like resonant perfect absorption. However, the utility of ENZ modes in nanophotonic applications has been limited by a flat spectral dispersion, which leads to small group velocities and extremely short propagation lengths. Here, we overcome this constraint by hybridizing ENZ and surface plasmon polariton (SPP) modes in doped cadmium oxide epitaxial bilayers. This results in strongly coupled hybrid modes that are characterized by an anticrossing in the polariton dispersion and a large spectral splitting on the order of 1/3 of the mode frequency. These hybrid modes simultaneously achieve modal propagation and ENZ mode-like interior field confinement, adding propagation character to ENZ mode properties. We subsequently tune the resonant frequencies, dispersion, and coupling of these polaritonic-hybrid-epsilon-near-zero (PH-ENZ) modes by tailoring the modal oscillator strength and the ENZ-SPP spectral overlap. PH-ENZ modes ultimately leverage the most desirable characteristics of both ENZ and SPP modes, allowing us to overcome the canonical plasmonic trade-off between confinement and propagation length.}, number={2}, journal={NANO LETTERS}, author={Runnerstrom, Evan L. and Kelley, Kyle P. and Folland, Thomas G. and Nolen, J. Ryan and Engheta, Nader and Caldwell, Joshua D. and Maria, Jon-Paul}, year={2019}, month={Feb}, pages={948–957} }
 @misc{khamh_sachet_kelly_maria_franzen_2018, title={As good as gold and better: conducting metal oxide materials for mid-infrared plasmonic applications}, volume={6}, ISSN={["2050-7534"]}, DOI={10.1039/c7tc05760a}, abstractNote={Review of material properties of conducting metal oxides that make them suitable for mid-infrared surface plasmon resonance applications.}, number={31}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, author={Khamh, Hniang and Sachet, Edward and Kelly, Kyle and Maria, Jon-Paul and Franzen, Stefan}, year={2018}, month={Aug}, pages={8326–8342} }
 @article{braun_rost_lim_giri_olson_kotsonis_stan_brenner_maria_hopkins_2018, title={Charge-Induced Disorder Controls the Thermal Conductivity of Entropy-Stabilized Oxides}, volume={30}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201805004}, abstractNote={Abstract}, number={51}, journal={ADVANCED MATERIALS}, author={Braun, Jeffrey L. and Rost, Christina M. and Lim, Mina and Giri, Ashutosh and Olson, David H. and Kotsonis, George N. and Stan, Gheorghe and Brenner, Donald W. and Maria, Jon-Paul and Hopkins, Patrick E.}, year={2018}, month={Dec} }
 @article{grimley_wynn_kelley_sachet_dean_freeman_maria_lebeau_2018, title={Complexities of atomic structure at CdO/MgO and CdO/Al2O3 interfaces}, volume={124}, ISSN={["1089-7550"]}, DOI={10.1063/1.5053752}, abstractNote={We report the interface structures of CdO thin films on 001-MgO and 0001-Al2O3 substrates. Using aberration corrected scanning transmission electron microscopy, we show that epitaxial growth of (001)-CdO∥(001)-MgO occurs with a lattice misfit greater than 10%. A high density of interface misfit dislocations is found to form. In combination with molecular dynamics simulations, we show that dislocation strain fields form and overlap in very thin heterostructures of CdO and MgO (<3 nm). On the c-Al2O3 substrate, we find that CdO grows with a surface normal of 025. We show that three rotation variants form due to the symmetry of the sapphire surface. These results contribute insights into the epitaxial growth of these rock-salt oxides.}, number={20}, journal={JOURNAL OF APPLIED PHYSICS}, author={Grimley, Everett D. and Wynn, Alex P. and Kelley, Kyle P. and Sachet, Edward and Dean, Julian S. and Freeman, Colin L. and Maria, Jon-Paul and LeBeau, James M.}, year={2018}, month={Nov} }
 @article{king_el-hinnawy_borodulin_ezis_luu_salmon_gu_nichols_dickey_maria_et al._2018, title={Connecting post-pulsing electrical and microstructural features in GeTe-based inline phase change switches}, volume={124}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.5031840}, DOI={10.1063/1.5031840}, abstractNote={Plan view scanning transmission electron microscopy was used to investigate the microstructural connections to device resistance in inline phase change switch devices. It was revealed that massive structural changes occur in GeTe during switching, most notably the formation of an assembly of voids along the device centerline and large GeTe grains on either side of an “active region.” Restructuring of this variety was tied to changes in ON-state resistance with increasing pulse number, where initially porous and fine-grained (10-20 nm) GeTe was converted to large crystalline domains comprising the majority of the RF gap (400-700 nm). A phenomenological model for this microstructure is presented in which the OFF pulse melts a given width of GeTe, and upon cooling crystalline material outside the melt region acts as a template for an inward-propagating crystalline growth front. The voids observed along the device centerline were correlated to increasing OFF state resistance and a relatively stable ON state with increasing pulse number via a series resistance model. As a result of this analysis, OFF state resistance was suggested as an early indicator of device reliability. An improved GeTe deposition process was implemented to limit void formation, which is shown to have a more stable OFF-state resistance with increasing pulse number.}, number={19}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={King, Matthew R. and El-Hinnawy, Nabil and Borodulin, Pavel and Ezis, Andy and Luu, Vivien and Salmon, Mike and Gu, Jitty and Nichols, Doyle T. and Dickey, Elizabeth and Maria, Jon-Paul and et al.}, year={2018}, month={Nov}, pages={195103} }
 @article{kotsonis_rost_harris_maria_2018, title={Epitaxial entropy-stabilized oxides: growth of chemically diverse phases via kinetic bombardment}, volume={8}, ISSN={["2159-6867"]}, DOI={10.1557/mrc.2018.184}, abstractNote={This paper explores thin films of the entropy-stabilized oxide (ESO) composition Mg_xNi_xCo_xCuxZn_xSc_xO (x~ 0.167) grown by laser ablation in incremental gas pressures and O_2/Ar ratios to modulate particle kinetic energy and plume reactivity. Low pressures supporting high kinetic energy adatoms favor the kinetic stabilization of a single rocksalt phase, while high pressures (low kinetic energy adatoms) result in phase separation. The pressure threshold for phase separation is a function of O_2/Ar ratio. These findings suggest large kinetic energies facilitate the assembly and quench of metastable ESO phases that may require immoderate physical or chemical conditions to synthesize using near-equilibrium techniques.}, number={3}, journal={MRS COMMUNICATIONS}, author={Kotsonis, George N. and Rost, Christina M. and Harris, David T. and Maria, Jon-Paul}, year={2018}, month={Sep}, pages={1371–1377} }
 @article{rak_maria_brenner_2018, title={Evidence for Jahn-Teller compression in the (Mg, Co, Ni, Cu, Zn)O entropy-stabilized oxide: A DFT study}, volume={217}, ISSN={["1873-4979"]}, DOI={10.1016/j.matlet.2018.01.111}, abstractNote={The local atomic configuration and the electronic structure of the octahedral Cu2+ centers in the entropy-stabilized oxides (ESOs), (MgCoNiZn)1−xCuxO (x = 0.13, 0.2, 0,.26), have been investigated using density functional theory. The calculated Cu–O bond lengths combined with the analysis of the electronic density of states indicate that ∼10% of the CuO6 octahedra in ESOs undergo Jahn-Teller (JT) compression. This unexpected behavior is likely related to the structural constraints imposed by the rocksalt lattice and reflects the competition between the regular octahedral environment preferred by the cations in the system and the JT distortion imposed by the Cu-centers. The orientation of the distortions appears to be random, in agreement with recent experimental results.}, journal={MATERIALS LETTERS}, author={Rak, Zs. and Maria, J. -P. and Brenner, D. W.}, year={2018}, month={Apr}, pages={300–303} }
 @inproceedings{matveev_basset_dlott_lee_maria_2018, title={High throughput investigation of shocked reactive nanolaminates}, url={http://dx.doi.org/10.1063/1.5044984}, DOI={10.1063/1.5044984}, abstractNote={Reactivity at the interface between an oxidizer and a metal fuel (CuO/Zr) initiated by an 8 ns duration planar shock wave was studied using a tabletop laser-driven flyer plate apparatus with high-speed emission spectroscopy and photon Doppler velocimetry. The reaction threshold was at an impact velocity of about 0.6 km/s. From the time-dependence of the emission produced at different flyer velocities, together with measurements on reactive nanolayer samples with different numbers of interfaces, we showed we can see a prompt interfacial reaction between prepositioned reagents and a bulk reaction. The interfacial reaction occurs in 100 ns, and the bulk reaction, which is thickness dependent, in 30 µs.}, publisher={Author(s)}, author={Matveev, Sergey M. and Basset, Will P. and Dlott, Dana D. and Lee, Evyn and Maria, Jon-Paul}, year={2018} }
 @article{sarker_harrington_toher_oses_samiee_maria_brenner_vecchio_curtarolo_2018, title={High-entropy high-hardness metal carbides discovered by entropy descriptors}, volume={9}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-018-07160-7}, abstractNote={Abstract}, journal={NATURE COMMUNICATIONS}, author={Sarker, Pranab and Harrington, Tyler and Toher, Cormac and Oses, Corey and Samiee, Mojtaba and Maria, Jon-Paul and Brenner, Donald W. and Vecchio, Kenneth S. and Curtarolo, Stefano}, year={2018}, month={Nov} }
 @article{radue_tomko_giri_braun_zhou_prezhdo_runnerstrom_maria_hopkins_2018, title={Hot Electron Thermoreflectance Coefficient of Gold during Electron-Phonon Nonequilibrium}, volume={5}, ISSN={["2330-4022"]}, DOI={10.1021/acsphotonics.8b01045}, abstractNote={The temperature-dependent reflectivity of metals is quantified by the thermoreflectance coefficient, which is a material-dependent parameter that depends on the metallic band structure, electron scattering dynamics, and photon wavelength. After short-pulse laser heating, the electronic subsystem in a metal can be driven to temperatures much higher than that of the lattice, which gives rise to unique nonequilibrium electron and phonon scattering dynamics, leading to a “hot electron” thermoreflectance that is different from the traditionally measured equilibrium coefficient. In this work, we analytically quantify and experimentally measure this hot electron thermoreflectance coefficient through ultrafast pump–probe measurements of thin gold films on silica glass and sapphire substrates. We demonstrate the ability to not only quantify the thermoreflectance during electron–phonon nonequilibrium but also validate this coefficient’s predicted dependence on the absolute temperature of the electronic subsystem. T...}, number={12}, journal={ACS PHOTONICS}, author={Radue, Elizabeth L. and Tomko, John A. and Giri, Ashutosh and Braun, Jeffrey L. and Zhou, Xin and Prezhdo, Oleg V. and Runnerstrom, Evan L. and Maria, Jon-Paul and Hopkins, Patrick E.}, year={2018}, month={Dec}, pages={4880–4887} }
 @article{paisley_brumbach_shelton_allerman_atcitty_rost_ohlhausen_doyle_sitar_maria_et al._2018, title={Nitride surface chemistry influence on band offsets at epitaxial oxide/GaN interfaces}, volume={112}, ISSN={["1077-3118"]}, DOI={10.1063/1.5013605}, abstractNote={GaN surface and near-surface chemistry influence on band offsets of oxide overlayers is demonstrated through X-ray photoelectron spectroscopy measurements using epitaxial (111)-oriented MgO films on (0001)-oriented Ga-polar GaN as a case study. For identical cleaning and MgO growth conditions, GaN subsurface oxygen impurities influence the GaN bare surface band bending and the ultimate band offset to MgO heterolayers. As the GaN surface oxygen concentration increases from an atomic concentration of 0.9% to 3.4%, the valence band offset to MgO decreases from 1.68 eV to 1.29 eV, respectively. This study highlights the sensitivity of the oxide/nitride interface electronic structure to GaN epilayer preparation and growth conditions.}, number={9}, journal={APPLIED PHYSICS LETTERS}, author={Paisley, Elizabeth A. and Brumbach, Michael T. and Shelton, Christopher T. and Allerman, Andrew A. and Atcitty, Stanley and Rost, Christina M. and Ohlhausen, James A. and Doyle, Barney L. and Sitar, Zlatko and Maria, Jon-Paul and et al.}, year={2018}, month={Feb} }
 @article{gaskins_kotsonis_giri_ju_rohskopf_wang_bai_sachet_shelton_liu_et al._2018, title={Thermal Boundary Conductance Across Heteroepitaxial ZnO/GaN Interfaces: Assessment of the Phonon Gas Model}, volume={18}, ISSN={["1530-6992"]}, DOI={10.1021/acs.nanolett.8b02837}, abstractNote={We present experimental measurements of the thermal boundary conductance (TBC) from 78-500 K across isolated heteroepitaxially grown ZnO films on GaN substrates. This data provides an assessment of the underlying assumptions driving phonon gas-based models, such as the diffuse mismatch model (DMM), and atomistic Green's function (AGF) formalisms used to predict TBC. Our measurements, when compared to previous experimental data, suggest that TBC can be influenced by long wavelength, zone center modes in a material on one side of the interface as opposed to the '"vibrational mismatch"' concept assumed in the DMM; this disagreement is pronounced at high temperatures. At room temperature, we measure the ZnO/GaN TBC as 490[+150,-110] MW m-2 K-1. The disagreement among the DMM and AGF, and the experimental data at elevated temperatures, suggests a non-negligible contribution from other types of modes that are not accounted for in the fundamental assumptions of these harmonic based formalisms, which may rely on anharmonicity. Given the high quality of these ZnO/GaN interfaces, these results provide an invaluable, critical, and quantitative assessment of the accuracy of assumptions in the current state of the art computational approaches used to predict phonon TBC across interfaces.}, number={12}, journal={NANO LETTERS}, author={Gaskins, John T. and Kotsonis, George and Giri, Ashutosh and Ju, Shenghong and Rohskopf, Andrew and Wang, Yekan and Bai, Tingyu and Sachet, Edward and Shelton, Christopher T. and Liu, Zeyu and et al.}, year={2018}, month={Dec}, pages={7469–7477} }
 @article{ceglia_scalora_vincenti_campione_kelley_runnerstrom_maria_keeler_luk_2018, title={Viscoelastic optical nonlocality of low-loss epsilon-near-zero nanofilms}, volume={8}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-018-27655-z}, abstractNote={Abstract}, journal={SCIENTIFIC REPORTS}, author={Ceglia, Domenico and Scalora, Michael and Vincenti, Maria A. and Campione, Salvatore and Kelley, Kyle and Runnerstrom, Evan L. and Maria, Jon-Paul and Keeler, Gordon A. and Luk, Ting S.}, year={2018}, month={Jun} }
 @article{maria_kang_floyd_dickey_guo_guo_baker_funihashi_randall_2017, title={Cold sintering: Current status and prospects}, volume={32}, ISSN={0884-2914 2044-5326}, url={http://dx.doi.org/10.1557/jmr.2017.262}, DOI={10.1557/jmr.2017.262}, abstractNote={Abstract}, number={17}, journal={Journal of Materials Research}, publisher={Cambridge University Press (CUP)}, author={Maria, Jon-Paul and Kang, Xiaoyu and Floyd, Richard D. and Dickey, Elizabeth C. and Guo, Hanzheng and Guo, Jing and Baker, Amanda and Funihashi, Shuichi and Randall, Clive A.}, year={2017}, month={Jul}, pages={3205–3218} }
 @article{ihlefeld_michael_mckenzie_scrymgeour_maria_paisley_kitahara_2017, title={Domain imaging in ferroelectric thin films via channeling-contrast backscattered electron microscopy}, volume={52}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-016-0402-x}, abstractNote={Ferroelastic domain walls provide opportunities for deterministically controlling mechanical, optical, electrical, and thermal energy. Domain wall characterization in micro- and nanoscale systems, where their spacing may be of the order of 100 nm or less is presently limited to only a few techniques, such as piezoresponse force microscopy and transmission electron microscopy. These respective techniques cannot, however, independently characterize domain polarization orientation and domain wall motion in technologically relevant capacitor structures or in a non-destructive manner, thus presenting a limitation of their utility. In this work, we show how backscatter scanning electron microscopy utilizing channeling contrast yield can image the ferroelastic domain structure of ferroelectric films with domain wall spacing as narrow as 10 nm. Combined with electron backscatter diffraction to identify grain orientations, this technique provides information on domain orientation and domain wall type that cannot be readily measured using conventional non-destructive methods. In addition to grain orientation identification, this technique enables dynamic domain structure changes to be observed in functioning capacitors utilizing electrodes that are transparent to the high-energy backscattered electrons. This non-destructive, high-resolution domain imaging technique is applicable to a wide variety of ferroelectric thin films and a multitude of material systems where nanometer-scale crystallographic twin characterization is required.}, number={2}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Ihlefeld, Jon F. and Michael, Joseph R. and McKenzie, Bonnie B. and Scrymgeour, David A. and Maria, Jon-Paul and Paisley, Elizabeth A. and Kitahara, Andrew R.}, year={2017}, month={Jan}, pages={1071–1081} }
 @article{kang_shetty_garten_ihlefeld_trolier-mckinstry_maria_2017, title={Enhanced dielectric and piezoelectric responses in Zn1-xMgxO thin films near the phase separation boundary}, volume={110}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4973756}, DOI={10.1063/1.4973756}, abstractNote={Dielectric and piezoelectric properties for Zn1-xMgxO (ZMO) thin films are reported as a function of MgO composition up to and including the phase separation region. Zn1-xMgxO (0.25 ≤ x ≤ 0.5) thin films with c-axis textures were deposited by pulsed laser deposition on platinized sapphire substrates. The films were phase pure wurtzite for MgO concentrations up to 40%; above that limit, a second phase with rocksalt structure evolves with strong {100} texture. With increasing MgO concentration, the out-of-plane (d33,f) and in-plane (e31,f) piezoelectric coefficients increase by 360% and 290%, respectively. The increase in piezoelectric coefficients is accompanied by a 35% increase in relative permittivity. Loss tangent values fall monotonically with increasing MgO concentration, reaching a minimum of 0.001 for x ≥ 0.30, at which point the band gap is reported to be 4 eV. The enhanced piezoelectric response, the large band gap, and the low dielectric loss make Zn1-xMgxO an interesting candidate for thin film piezoelectric devices, and demonstrate that compositional phase transformations provide opportunities for property engineering.}, number={4}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Kang, Xiaoyu and Shetty, Smitha and Garten, Lauren and Ihlefeld, Jon F. and Trolier-McKinstry, Susan and Maria, Jon-Paul}, year={2017}, month={Jan}, pages={042903} }
 @article{runnerstrom_kelley_sachet_shelton_maria_2017, title={Epsilon-near-Zero Modes and Surface Plasmon Resonance in Fluorine-Doped Cadmium Oxide Thin Films}, volume={4}, ISSN={["2330-4022"]}, DOI={10.1021/acsphotonics.7b00429}, abstractNote={In this report we demonstrate fluorine-doped CdO as a model infrared plasmonic material by virtue of its tunable carrier density, high mobility, and intense extreme-subwavelength plasmon–polariton coupling. Carrier concentrations ranging from 1019 to 1020 cm–3, with electron mobility values as high as 473 cm2/V·s, are readily achieved in epitaxial CdO films over a thickness range spanning 50 to 500 nm. Carrier concentration is achieved by reactive sputtering in an Ar/O2 atmosphere with trace quantities of CF4. Infrared reflectometry measurements demonstrate the possibility of near-perfect plasmonic absorption through the entire mid-IR spectral range. A companion set of reflectivity simulations are used to predict, understand, and optimize the epsilon-near-zero plasmonic modes. In the context of other transparent conductors, CdO exhibits substantially higher electron mobility values and thus sharp and tunable absorption features. This highlights the utility of high-mobility transparent conducting oxides as...}, number={8}, journal={ACS PHOTONICS}, author={Runnerstrom, Evan L. and Kelley, Kyle P. and Sachet, Edward and Shelton, Christopher T. and Maria, Jon-Paul}, year={2017}, month={Aug}, pages={1885–1892} }
 @article{yang_kelley_sachet_campione_luk_maria_sinclair_brener_2017, title={Femtosecond optical polarization switching using a cadmium oxide-based perfect absorber}, volume={11}, ISSN={1749-4885 1749-4893}, url={http://dx.doi.org/10.1038/NPHOTON.2017.64}, DOI={10.1038/NPHOTON.2017.64}, abstractNote={Ultrafast control of the polarization state of light may enable a plethora of applications in optics, chemistry and biology. However, conventional polarizing elements, such as polarizers and waveplates, are either static or possess only gigahertz switching speeds. Here, with the aid of high-mobility indium-doped cadmium oxide (CdO) as the gateway plasmonic material, we realize a high-quality factor Berreman-type perfect absorber at a wavelength of 2.08 μm. On sub-bandgap optical pumping, the perfect absorption resonance strongly redshifts because of the transient increase of the ensemble-averaged effective electron mass of CdO, which leads to an absolute change in the p-polarized reflectance from 1.0 to 86.3%. By combining the exceedingly high modulation depth with the polarization selectivity of the perfect absorber, we experimentally demonstrate a reflective polarizer with a polarization extinction ratio of 91 that can be switched on and off within 800 fs. Indium-doped cadmium oxide performs polarization switching on a subpicosecond timescale.}, number={6}, journal={Nature Photonics}, publisher={Springer Science and Business Media LLC}, author={Yang, Yuanmu and Kelley, Kyle and Sachet, Edward and Campione, Salvatore and Luk, Ting S. and Maria, Jon-Paul and Sinclair, Michael B. and Brener, Igal}, year={2017}, month={May}, pages={390–395} }
 @article{rost_braun_ferri_backman_giri_opila_maria_hopkins_2017, title={Hafnium nitride films for thermoreflectance transducers at high temperatures: Potential based on heating from laser absorption}, volume={111}, ISSN={["1077-3118"]}, DOI={10.1063/1.5006648}, abstractNote={Time domain thermoreflectance (TDTR) and frequency domain thermoreflectance (FDTR) are common pump-probe techniques that are used to measure the thermal properties of materials. At elevated temperatures, transducers used in these techniques can become limited by melting or other phase transitions. In this work, time domain thermoreflectance is used to determine the viability of HfN thin film transducers grown on SiO2 through measurements of the SiO2 thermal conductivity up to approximately 1000 K. Further, the reliability of HfN as a transducer is determined by measuring the thermal conductivities of MgO, Al2O3, and diamond at room temperature. The thermoreflectance coefficient of HfN was found to be 1.4 × 10−4 K−1 at 800 nm, one of the highest thermoreflectance coefficients measured at this standard TDTR probe wavelength. Additionally, the high absorption of HfN at 400 nm is shown to enable reliable laser heating to elevate the sample temperature during a measurement, relative to other transducers.}, number={15}, journal={APPLIED PHYSICS LETTERS}, author={Rost, Christina M. and Braun, Jeffrey and Ferri, Kevin and Backman, Lavina and Giri, Ashutosh and Opila, Elizabeth J. and Maria, Jon-Paul and Hopkins, Patrick E.}, year={2017}, month={Oct} }
 @article{kelley_sachet_shelton_maria_2017, title={High mobility yttrium doped cadmium oxide thin films}, volume={5}, ISSN={["2166-532X"]}, DOI={10.1063/1.4993799}, abstractNote={Donor doped CdO thin films on c-plane sapphire are prepared by reactive co-sputtering from Cd-metal and Y-metal targets which are driven using pulsed-dc and RF power respectively. Intrinsic CdO exhibits a carrier density of 1.8 × 1019 cm−3 and a mobility of 330 cm2 V−1 s−1. By increasing the Y-flux, carrier density values can be increased smoothly and reproducibly to a maximum value of 3.3 × 1020 cm−3. Mobility increases with Y flux, and exhibits a broad plateau between approximately 5 × 1019 cm−3 and 2 × 1020 cm−3. Higher carrier concentrations produce a sharp drop in mobility. The increase in mobility is attributed to a reduction of intrinsic donors (i.e., oxygen vacancies) with increasing carrier density while the ultimate decrease in mobility results from a combination of factors including cadmium vacancies, reduced crystal quality, and smaller crystallite sizes, all of which accompany carrier density values greater than the mid 1020 cm−3 range. This work demonstrates that CdO thin films can be prepared by magnetron sputtering with transport properties and crystal quality that are comparable to those grown using molecular beam epitaxy.}, number={7}, journal={APL MATERIALS}, author={Kelley, Kyle P. and Sachet, Edward and Shelton, Christopher T. and Maria, Jon-Paul}, year={2017}, month={Jul} }
 @inproceedings{yang_kelly_sachet_campione_luk_maria_brener_2017, title={High-contrast, all-optical switching of infrared light using a cadmium oxide perfect absorber}, DOI={10.1364/cleo_qels.2017.fm2h.4}, abstractNote={We experimentally demonstrate high-contrast, ultrafast switching of infrared light at 2.1 μm via intraband pumping of a high quality factor perfect absorber made from a highly doped cadmium oxide thin film.}, booktitle={2017 conference on lasers and electro-optics (cleo)}, author={Yang, Y. M. and Kelly, K. and Sachet, E. and Campione, S. and Luk, T. S. and Maria, J. P. and Brener, I.}, year={2017} }
 @article{rost_rak_brenner_maria_2017, title={Local structure of the MgxNixCoxCuxZnxO(x=0.2) entropy-stabilized oxide: An EXAFS study}, volume={100}, ISSN={["1551-2916"]}, DOI={10.1111/jace.14756}, abstractNote={Abstract}, number={6}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Rost, Christina M. and Rak, Zsolt and Brenner, Donald W. and Maria, Jon-Paul}, year={2017}, month={Jun}, pages={2732–2738} }
 @article{diercks_brennecka_gorman_rost_maria_2017, title={Nanoscale Compositional Analysis of a Thermally Processed Entropy-Stabilized Oxide via Correlative TEM and APT}, volume={23}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927617008868}, DOI={10.1017/S1431927617008868}, abstractNote={The recent demonstration of entropy-stabilized oxides (ESOs) [1] suggests new avenues for controlling the microstructures and, thus, properties within this new family of oxide ceramics through a combination of composition control and thermal processing. In order to better understand the possibilities for engineering specific properties, a detailed understanding at the atomic scale is desirable.}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Diercks, David R. and Brennecka, Geoff and Gorman, Brian P. and Rost, Christina M. and Maria, Jon-Paul}, year={2017}, month={Jul}, pages={1640–1641} }
 @inproceedings{ceglia_scalora_vincenti_campione_kelley_maria_keeler_luk_2017, title={Observation of nonlocal optical response in doped-cadmium-oxide epsilon-near-zero thin films}, DOI={10.1109/iceaa.2017.8065557}, abstractNote={We study optically-excited nonlocalities in thin films of doped cadmium oxide. Although these effects are usually weak and hardly observable in the optical response of noble metals, the free-electron nonlocality is significantly increased in doped-cadmium-oside thin films. This increase is due mainly to: (i) low electron scattering rates; and (ii) interband transitions due to valence-band and inner-core electrons that occur far from the epsilon-near-zero frequency. The optical nonlocality manifests itself in the blueshift of the epsilon-near-zero mode, an associated reflectance dip, and the onset of higher-order modes. We model the structure using a generalized hydrodynamic theory that treats the free electrons in the film as a viscoelastic fluid. We demonstrate that both elasticity and viscosity play a significant role in the optical response of the film. The elasticity induces optical resonances associated with the longitudinal pressure modes of the free-electrons fluid, leading to a thickness-dependent permittivity. The viscosity introduces nonlocal damping and additional losses. In our view, this demonstration furthers our understanding of the dynamics of light-matter interactions, and adds a significant stepping stone toward the ability to effectively manipulate linear and nonlinear optical properties at the nanoscale.}, booktitle={2017 International Conference on Electromagnetics in Advanced Applications (ICEAA)}, author={Ceglia, D. and Scalora, M. and Vincenti, M. A. and Campione, S. and Kelley, K. and Maria, J. P. and Keeler, G. A. and Luk, T. S.}, year={2017}, pages={1462–1464} }
 @article{shelton_bryan_paisley_sachet_ihlefeld_lavrik_collazo_sitar_maria_2017, title={Step-free GaN surfaces grown by confined-area metal-organic vapor phase epitaxy}, volume={5}, ISSN={["2166-532X"]}, DOI={10.1063/1.4993840}, abstractNote={A two-step homoepitaxial growth process producing step-free surfaces on low dislocation density, Ga-polar ammonothermal GaN single crystals is described. Growth is conducted under very low supersaturation conditions where adatom incorporation occurs predominantly at step edges, and lateral growth is strongly preferred. The achievable step-free area is limited by the substrate dislocation density. For ammonothermal crystals with an average dislocation density of ∼1 × 104 cm−2, step-free mesas up to 200 × 200 μm2 in size are achieved. These remarkable surfaces create a unique opportunity to study the effect of steps on the properties and performance of semiconductor heterostructures.}, number={9}, journal={APL MATERIALS}, author={Shelton, Christopher T. and Bryan, Isaac and Paisley, Elizabeth A. and Sachet, Edward and Ihlefeld, Jon F. and Lavrik, Nick and Collazo, Ramon and Sitar, Zlatko and Maria, Jon-Paul}, year={2017}, month={Sep} }
 @article{faber_asefa_backhaus-ricoult_brow_chan_dillon_fahrenholtz_finnis_garay_garcia_et al._2017, title={The role of ceramic and glass science research in meeting societal challenges: Report from an NSF-sponsored workshop}, volume={100}, ISSN={["1551-2916"]}, DOI={10.1111/jace.14881}, abstractNote={Abstract}, number={5}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Faber, Katherine T. and Asefa, Tewodros and Backhaus-Ricoult, Monika and Brow, Richard and Chan, Julia Y. and Dillon, Shen and Fahrenholtz, William G. and Finnis, Michael W. and Garay, Javier E. and Garcia, R. Edwin and et al.}, year={2017}, month={May}, pages={1777–1803} }
 @article{rak_rost_lim_sarker_toher_curtarolo_maria_brenner_2016, title={Charge compensation and electrostatic transferability in three entropy-stabilized oxides: Results from density functional theory calculations}, volume={120}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.4962135}, DOI={10.1063/1.4962135}, abstractNote={Density functional theory calculations were carried out for three entropic rocksalt oxides, (Mg0.1Co0.1Ni0.1Cu0.1Zn0.1)O0.5, termed J14, and J14 + Li and J14 + Sc, to understand the role of charge neutrality and electronic states on their properties, and to probe whether simple expressions may exist that predict stability. The calculations predict that the average lattice constants of the ternary structures provide good approximations to that of the random structures. For J14, Bader charges are transferable between the binary, ternary, and random structures. For J14 + Sc and J14 + Li, average Bader charges in the entropic structures can be estimated from the ternary compositions. Addition of Sc to J14 reduces the majority of Cu, which show large displacements from ideal lattice sites, along with reduction of a few Co and Ni cations. Addition of Li to J14 reduces the lattice constant, consistent with experiment, and oxidizes some of Co as well as some of Ni and Cu. The Bader charges and spin-resolved density of states (DOS) for Co+3 in J14 + Li are very different from Co+2, while for Cu and Ni the Bader charges form continuous distributions and the two DOS are similar for the two oxidation states. Experimental detection of different oxidation states may therefore be challenging for Cu and Ni compared to Co. Based on these results, empirical stability parameters for these entropic oxides may be more complicated than those for non-oxide entropic solids.}, number={9}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Rak, Zs. and Rost, C. M. and Lim, M. and Sarker, P. and Toher, C. and Curtarolo, S. and Maria, J.-P. and Brenner, D. W.}, year={2016}, month={Sep}, pages={095105} }
 @article{meyer_cheaito_paisley_shelton_braun_maria_ihlefeld_hopkins_2016, title={Crystalline coherence length effects on the thermal conductivity of MgO thin films}, volume={51}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-016-0261-5}, number={23}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Meyer, Kelsey E. and Cheaito, Ramez and Paisley, Elizabeth and Shelton, Christopher T. and Braun, Jeffrey L. and Maria, Jon-Paul and Ihlefeld, Jon F. and Hopkins, Patrick E.}, year={2016}, month={Dec}, pages={10408–10417} }
 @article{donovan_sachet_maria_hopkins_2016, title={Interplay between mass-impurity and vacancy phonon scattering effects on the thermal conductivity of doped cadmium oxide}, volume={108}, ISSN={["1077-3118"]}, DOI={10.1063/1.4939652}, abstractNote={Understanding the impact and complex interaction of thermal carrier scattering centers in functional oxide systems is critical to their progress and application. In this work, we study the interplay among electron and phonon thermal transport, mass-impurity scattering, and phonon-vacancy interactions on the thermal conductivity of cadmium oxide. We use time domain thermoreflectance to measure the thermal conductivity of a set of CdO thin films doped with Dy up to the saturation limit. Using measurements at room temperature and 80 K, our results suggest that the enhancement in thermal conductivity at low Dy concentrations is dominated by an increase in the electron mobility due to a decrease in oxygen vacancy concentration. Furthermore, we find that at intermediate doping concentrations, the subsequent decrease in thermal conductivity can be ascribed to a large reduction in phononic thermal transport due to both point defect and cation-vacancy scattering. With these results, we gain insight into the complex dynamics driving phonon scattering and resulting thermal transport in functional oxides.}, number={2}, journal={APPLIED PHYSICS LETTERS}, author={Donovan, Brian F. and Sachet, Edward and Maria, Jon-Paul and Hopkins, Patrick E.}, year={2016}, month={Jan} }
 @article{harris_burch_mily_dickey_maria_2016, title={Microstructure and dielectric properties with CuO additions to liquid phase sintered BaTiO3 thin films}, volume={31}, ISSN={0884-2914 2044-5326}, url={http://dx.doi.org/10.1557/jmr.2016.89}, DOI={10.1557/jmr.2016.89}, abstractNote={Abstract}, number={8}, journal={Journal of Materials Research}, publisher={Cambridge University Press (CUP)}, author={Harris, David T. and Burch, Matthew J. and Mily, Edward J. and Dickey, Elizabeth C. and Maria, Jon-Paul}, year={2016}, month={Mar}, pages={1018–1026} }
 @article{kang_losego_sachet_maria_franzen_2016, title={Near-Infrared Optical Extinction of Indium Tin Oxide Structures Prepared by Nanosphere Lithography}, volume={3}, ISSN={["2330-4022"]}, DOI={10.1021/acsphotonics.6b00649}, abstractNote={Indium tin oxide (ITO) has been the most widely studied conducting metal oxide and serves as the best candidate for proof-of-concept experiments in the field of surface plasmon resonance and studies of electric field confinement and manipulation. ITO is chemically stable and relatively easy to sputter. In this report, arrays of ITO nanostructures were produced using nanosphere lithography, which was originally developed for plasmonic applications involving noble metals. However, the experiments presented here show that patterned ITO with similar size and shape to noble metals has an observed extinction that corresponds to the epsilon-near-zero mode. The carrier density of ITO nanostructure can be controlled by the postdeposition annealing process. Thus, one can prove that the optical signals on the surface are those of the ITO nanostructure by reversible on/off switching of the capacitive plasmon resonance by annealing the surfaces successively in forming gas (N2/H2) and in air. Thus, using conducting met...}, number={10}, journal={ACS PHOTONICS}, author={Kang, Misun and Losego, Mark and Sachet, Edward and Maria, Jon-Paul and Franzen, Stefan}, year={2016}, month={Oct}, pages={1993–1999} }
 @article{grimley_sachet_donovan_hopkins_maria_lebeau_2016, title={Observing Misfit Dislocation Interactions Across Thin Film Oxide Heterostructures}, volume={22}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927616008370}, DOI={10.1017/S1431927616008370}, abstractNote={Complete realization of next-generation plasmonic devices has been plagued by the high dielectric losses and the limited spectral regime of traditional noble metal plasmonic materials. Oxide semiconductors are poised to be suitable alternatives to traditional plasmonic materials, as oxides possess both low dielectric losses and tunable band gaps which are important properties for enhancing plasmonic performance. Recently, Sachet et al . showed that dysprosium doping of thin film CdO affords dramatic control over the film’s optical properties by altering the carrier concentration and carrier mobility [1]. This exciting discovery indicates that Dy:CdO is a suitable material for tunable use in the mid-IR plasmonic regime. CdO films are epitaxially grown on MgO substrates and possess a nearly 12% lattice mismatch with the substrate. Such a misfit is expected to be accompanied by interfacial dislocations to reduce strain. These dislocations and their associated strain fields are expected to play a further role in altering film conductivity and thermal properties, as they form scattering centers for charge carriers and phonons. This effect is expected to be more pronounced for thinner films. To examine the interplay between CdO film thermal properties and interfacial dislocations/strain, a thickness series of sub-10 nm CdO films were deposited on (001)-oriented MgO substrates and were capped with 10 nm of MgO. Dislocation ordering and the associated strain fields at top and bottom CdO/MgO interfaces were analyzed with scanning transmission electron microscopy (STEM). Micrographs were acquired using the RevSTEM technique to minimize drift distortion [2]. The images were acquired using low-angle annular dark-field (LAADF)-STEM with a probe-corrected FEI Titan G2 60-300 kV microscope operated at 200 kV with detector inner semi-angle and probe semi-convergence}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Grimley, Everett D. and Sachet, Edward and Donovan, Brian F. and Hopkins, Patrick E. and Maria, Jon-Paul and LeBeau, James M.}, year={2016}, month={Jul}, pages={1506–1507} }
 @article{ihlefeld_harris_keech_jones_maria_trolier-mckinstry_2016, title={Scaling Effects in Perovskite Ferroelectrics: Fundamental Limits and Process-Structure-Property Relations}, volume={99}, ISSN={["1551-2916"]}, DOI={10.1111/jace.14387}, abstractNote={Ferroelectric materials are well‐suited for a variety of applications because they can offer a combination of high performance and scaled integration. Examples of note include piezoelectrics to transform between electrical and mechanical energies, capacitors used to store charge, electro‐optic devices, and nonvolatile memory storage. Accordingly, they are widely used as sensors, actuators, energy storage, and memory components, ultrasonic devices, and in consumer electronics products. Because these functional properties arise from a noncentrosymmetric crystal structure with spontaneous strain and a permanent electric dipole, the properties depend upon physical and electrical boundary conditions, and consequently, physical dimension. The change in properties with decreasing physical dimension is commonly referred to as a size effect. In thin films, size effects are widely observed, whereas in bulk ceramics, changes in properties from the values of large‐grained specimens is most notable in samples with grain sizes below several micrometers. It is important to note that ferroelectricity typically persists to length scales of about 10 nm, but below this point is often absent. Despite the stability of ferroelectricity for dimensions greater than ~10 nm, the dielectric and piezoelectric coefficients of scaled ferroelectrics are suppressed relative to their bulk counterparts, in some cases by changes up to 80%. The loss of extrinsic contributions (domain and phase boundary motion) to the electromechanical response accounts for much of this suppression. In this article, the current understanding of the underlying mechanisms for this behavior in perovskite ferroelectrics is reviewed. We focus on the intrinsic limits of ferroelectric response, the roles of electrical and mechanical boundary conditions, grain size and thickness effects, and extraneous effects related to processing. In many cases, multiple mechanisms combine to produce the observed scaling effects.}, number={8}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Ihlefeld, Jon F. and Harris, David T. and Keech, Ryan and Jones, Jacob L. and Maria, Jon-Paul and Trolier-McKinstry, Susan}, year={2016}, month={Aug}, pages={2537–2557} }
 @article{losego_paisley_craft_lam_sachet_mita_collazo_sitar_maria_2016, title={Selective area epitaxy of magnesium oxide thin films on gallium nitride surfaces}, volume={31}, ISSN={["2044-5326"]}, DOI={10.1557/jmr.2015.332}, abstractNote={Abstract}, number={1}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Losego, Mark D. and Paisley, Elizabeth A. and Craft, H. Spalding and Lam, Peter G. and Sachet, Edward and Mita, Seiji and Collazo, Ramon and Sitar, Zlatko and Maria, Jon-Paul}, year={2016}, month={Jan}, pages={36–45} }
 @article{beechem_mcdonald_fuller_talin_rost_maria_gaskins_hopkins_allerman_2016, title={Size dictated thermal conductivity of GaN}, volume={120}, DOI={10.1063/1.4962010}, abstractNote={The thermal conductivity of n- and p-type doped gallium nitride (GaN) epilayers having thicknesses of 3–4 μm was investigated using time domain thermoreflectance. Despite possessing carrier concentrations ranging across 3 decades (1015–1018 cm–3), n-type layers exhibit a nearly constant thermal conductivity of 180 W/mK. The thermal conductivity of p-type epilayers, in contrast, reduces from 160 to 110 W/mK with increased doping. These trends—and their overall reduction relative to bulk—are explained leveraging established scattering models where it is shown that, while the decrease in p-type layers is partly due to the increased impurity levels evolving from its doping, size effects play a primary role in limiting the thermal conductivity of GaN layers tens of microns thick. Device layers, even of pristine quality, will therefore exhibit thermal conductivities less than the bulk value of 240 W/mK owing to their finite thickness.}, number={9}, journal={Journal of Applied Physics}, author={Beechem, T. E. and McDonald, A. E. and Fuller, E. J. and Talin, A. A. and Rost, C. M. and Maria, J. P. and Gaskins, J. T. and Hopkins, P. E. and Allerman, A. A.}, year={2016} }
 @article{bakker_ji_2016, title={The Construction of Compton Tensors in Scalar QED}, volume={58}, ISSN={0177-7963 1432-5411}, url={http://dx.doi.org/10.1007/S00601-016-1172-3}, DOI={10.1007/s00601-016-1172-3}, abstractNote={Current conservation is a vital condition in electrodynamics. We review the literature concerning the ways to ensure that the formalism used in calculating amplitudes for the scattering of charged particles is in compliance with current conservation. For the case of electron scattering off a scalar and a spin-1/2 target as well as Compton scattering on a scalar target, we present some novelties besides reviewing the literature.}, number={1}, journal={Few-Body Systems}, publisher={Springer Nature}, author={Bakker, Bernard L. G. and Ji, Chueng-Ryong}, year={2016}, month={Dec} }
 @article{bryan_bryan_mita_rice_hussey_shelton_tweedie_maria_collazo_sitar_2016, title={The role of surface kinetics on composition and quality of AlGaN}, volume={451}, ISSN={["1873-5002"]}, DOI={10.1016/j.jcrysgro.2016.06.055}, abstractNote={Metal–polar, Al-rich AlGaN films were grown on both single crystalline AlN and sapphire substrates. The role of surface morphology and surface kinetics on AlGaN composition is presented. With the reduced dislocation density of the films grown on AlN substrates, atomically smooth bilayer stepped surfaces are achieved with RMS roughness of less than 50 pm for a 5×5 µm2 AFM scan area. By controlling the surface supersaturation through adjusting the growth rate, a transition from 2D nucleation to step flow was observed. The critical misorientation angle for step-bunching in nominal Al0.70Ga0.30N grown with a growth rate of 600 nm/h on AlN substrates was found to be 0.4°. The composition of bilayer stepped AlGaN was strongly dependent on substrate misorientation angle, where a compositional variation by a factor of two for a change in misorientation angle from 0.05 to 0.40° was observed; this is explained by the different surface diffusion lengths of Ga and Al. Step-bunching resulted in strong compositional inhomogeneity as observed by photoluminescence and scanning transmission electron microscopy studies.}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Bryan, Isaac and Bryan, Zachary and Mita, Seiji and Rice, Anthony and Hussey, Lindsay and Shelton, Christopher and Tweedie, James and Maria, Jon-Paul and Collazo, Ramon and Sitar, Zlatko}, year={2016}, month={Oct}, pages={65–71} }
 @article{moballegh_rost_maria_dickey_2015, title={Chemical Homogeneity in Entropy-Stabilized Complex Metal Oxides}, volume={21}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927615007539}, DOI={10.1017/S1431927615007539}, abstractNote={Innovation in new mixtures of constituents can lead to discover exciting new materials with unexpected properties and revolutionary applications [1,2]. It is known, the Gibbs energy needs to be minimized, as the main requirement, to achieve a stable single phase compound. Conventional approach to minimize the total energy of system is searching for a large and negative enthalpy. However, in this work, we show that the phase stability can be reached where the configurational entropy is maximized with mixing as many diverse elements as possible.}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Moballegh, Ali and Rost, Christina M. and Maria, Jon-Paul and Dickey, Elizabeth C.}, year={2015}, month={Aug}, pages={1349–1350} }
 @article{burch_harris_fancher_maria_dickey_2015, title={Domain Structure of Bulk and Thin-Film Ferroelectrics By Transmission Kikuchi Diffraction}, volume={21}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927615004687}, DOI={10.1017/S1431927615004687}, abstractNote={Non-linear dielectrics are of great interest due to their integration into modern electronics, including tunable and memory devices [1]. Recently, much work has been invested into obtaining bulk-like properties of dielectric thin films at lower processing temperatures than are generally required for maximum performance. In particular, Harris et. al. has shown impressive dielectric properties of thin films at processing temperatures as low as 900°C for barium titanate (BaTiO3), contrasted with bulk, where similar properties would need 1250°C or higher processing temperatures [2].}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Burch, Matthew J. and Harris, David T. and Fancher, Chris M. and Maria, Jon-Paul and Dickey, Elizabeth C.}, year={2015}, month={Aug}, pages={777–778} }
 @article{sachet_shelton_harris_gaddy_irving_curtarolo_donovan_hopkins_sharma_sharma_et al._2015, title={Dysprosium-doped cadmium oxide as a gateway material for mid-infrared plasmonics}, volume={14}, ISSN={1476-1122 1476-4660}, url={http://dx.doi.org/10.1038/NMAT4203}, DOI={10.1038/nmat4203}, abstractNote={The interest in plasmonic technologies surrounds many emergent optoelectronic applications, such as plasmon lasers, transistors, sensors and information storage. Although plasmonic materials for ultraviolet-visible and near-infrared wavelengths have been found, the mid-infrared range remains a challenge to address: few known systems can achieve subwavelength optical confinement with low loss in this range. With a combination of experiments and ab initio modelling, here we demonstrate an extreme peak of electron mobility in Dy-doped CdO that is achieved through accurate 'defect equilibrium engineering'. In so doing, we create a tunable plasmon host that satisfies the criteria for mid-infrared spectrum plasmonics, and overcomes the losses seen in conventional plasmonic materials. In particular, extrinsic doping pins the CdO Fermi level above the conduction band minimum and it increases the formation energy of native oxygen vacancies, thus reducing their populations by several orders of magnitude. The substitutional lattice strain induced by Dy doping is sufficiently small, allowing mobility values around 500 cm(2) V(-1) s(-1) for carrier densities above 10(20) cm(-3). Our work shows that CdO:Dy is a model system for intrinsic and extrinsic manipulation of defects affecting electrical, optical and thermal properties, that oxide conductors are ideal candidates for plasmonic devices and that the defect engineering approach for property optimization is generally applicable to other conducting metal oxides.}, number={4}, journal={Nature Materials}, publisher={Springer Science and Business Media LLC}, author={Sachet, Edward and Shelton, Christopher T. and Harris, Joshua S. and Gaddy, Benjamin E. and Irving, Douglas L. and Curtarolo, Stefano and Donovan, Brian F. and Hopkins, Patrick E. and Sharma, Peter A. and Sharma, Ana Lima and et al.}, year={2015}, month={Feb}, pages={414–420} }
 @article{rost_sachet_borman_moballegh_dickey_hou_jones_curtarolo_maria_2015, title={Entropy-stabilized oxides}, volume={6}, ISSN={2041-1723}, url={http://dx.doi.org/10.1038/NCOMMS9485}, DOI={10.1038/NCOMMS9485}, abstractNote={Abstract}, number={1}, journal={Nature Communications}, publisher={Springer Science and Business Media LLC}, author={Rost, Christina M. and Sachet, Edward and Borman, Trent and Moballegh, Ali and Dickey, Elizabeth C. and Hou, Dong and Jones, Jacob L. and Curtarolo, Stefano and Maria, Jon-Paul}, year={2015}, month={Sep} }
 @article{harris_burch_li_dickey_maria_2015, title={Low‐Temperature Control of Twins and Abnormal Grain Growth in BaTiO
            3}, volume={98}, ISSN={0002-7820 1551-2916}, url={http://dx.doi.org/10.1111/jace.13643}, DOI={10.1111/jace.13643}, abstractNote={The microstructure of polycrystalline barium titanate (BaTiO3) thin films processed with a liquid‐phase can be controlled by the crystallographic orientation of the underlying sapphire substrate. During postdeposition crystallization, the tendency for {111} twin nucleation, which drives subsequent abnormal grain growth, depends upon the specific sapphire facet. Specifically, tilting away from the close‐packed c‐plane modifies the orientation, morphology, and relative amount of an interfacial BaAl2O4 second phase. These factors control the density of twin formation, and thus overall grain size of the crystallized BaTiO3. As the substrate orientation transitions from c‐plane, to r‐plane, to a‐plane, the twin density is reduced, the average grain size decreases systematically from 270 to 130 nm, and the grain structure becomes overall more homogeneous. This twinning mechanism and abnormal grain growth occur by 900°C, several hundred degrees lower than reported previously.}, number={8}, journal={Journal of the American Ceramic Society}, publisher={Wiley}, author={Harris, David T. and Burch, Matthew J. and Li, Jing and Dickey, Elizabeth C. and Maria, Jon‐Paul}, editor={Viehland, D.Editor}, year={2015}, month={May}, pages={2381–2387} }
 @article{lu_mily_irving_maria_brenner_2015, title={New Method for Extracting Diffusion-Controlled Kinetics from Differential Scanning Calorimetry: Application to Energetic Nanostructures}, volume={119}, ISSN={1932-7447 1932-7455}, url={http://dx.doi.org/10.1021/ACS.JPCC.5B03317}, DOI={10.1021/ACS.JPCC.5B03317}, abstractNote={A new expression is derived for interpreting differential scanning calorimetry curves for solid-state reactions with diffusion-controlled kinetics. The new form yields an analytic expression for temperature at the maximum peak height that is similar to a Kissinger analysis, but that explicitly accounts for laminar, cylindrical, and spherical multilayer system geometries. This expression was used to analyze two reactive multilayer nanolaminate systems, a Zr/CuO thermite and an Ni/Al aluminide, that include systematically varied layer thicknesses. This new analysis scales differential scanning calorimetry (DSC) peak temperatures against sample geometry, which leads to geometry-independent inherent activation energies and prefactors. For the Zr/CuO system, the DSC data scale with the square of the bilayer thickness, while, for the Ni/Al system, the DSC data scale with the thickness. This suggests distinct reaction mechanisms between these systems.}, number={25}, journal={The Journal of Physical Chemistry C}, publisher={American Chemical Society (ACS)}, author={Lu, Shijing and Mily, Edward J. and Irving, Douglas L. and Maria, Jon-Paul and Brenner, Donald W.}, year={2015}, month={Jun}, pages={150610143303004} }
 @article{egan_mily_maria_zachariah_2015, title={Probing the Reaction Dynamics of Thermite Nanolaminates}, volume={119}, ISSN={["1932-7447"]}, DOI={10.1021/acs.jpcc.5b04117}, abstractNote={Al/CuO reactive nanolaminate ignition was studied using temperature jump (T-Jump) heating for rates greater than 105 K/s. Multilayer samples were sputter deposited onto thin platinum filaments in alternating layers of Al and CuO. The filaments were resistively heated in a time-of-flight mass spectrometer (ToF-MS), while ignition and reaction were observed with high-speed video. A total deposited thickness of 1800 nm was maintained for all samples, while the number of bilayers was varied from 1 to 12. Increasing this value decreased the diffusion distances and increased the amount of interfacial area across which reaction could occur, while keeping the overall energy of the system constant. From 2 to 6 bilayers, the ignition temperature decreased from 1250 to 670 K and the overall reactivity increased. Past 6 bilayers, the ignition temperature only decreased slightly and there was little impact on the overall reactivity. This behavior is consistent with a mass-transport model where the predominant diffusin...}, number={35}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Egan, Garth C. and Mily, Edward J. and Maria, Jon-Paul and Zachariah, Michael R.}, year={2015}, month={Sep}, pages={20401–20408} }
 @article{kwon_huang_shu_yuan_maria_jiang_2014, title={Flexoelectricity in barium strontium titanate thin film}, volume={105}, ISSN={["1077-3118"]}, DOI={10.1063/1.4898139}, abstractNote={Flexoelectricity, the linear coupling between the strain gradient and the induced electric polarization, has been intensively studied as an alternative to piezoelectricity. Especially, it is of interest to develop flexoelectric devices on micro/nano scales due to the inherent scaling effect of flexoelectric effect. Ba0.7Sr0.3TiO3 thin film with a thickness of 130 nm was fabricated on a silicon wafer using a RF magnetron sputtering process. The flexoelectric coefficients of the prepared thin films were determined experimentally. It was revealed that the thin films possessed a transverse flexoelectric coefficient of 24.5 μC/m at Curie temperature (∼28 °C) and 17.44 μC/m at 41 °C. The measured flexoelectric coefficients are comparable to that of bulk BST ceramics, which are reported to be 10–100 μC/m. This result suggests that the flexoelectric thin film structures can be effectively used for micro/nano-sensing devices.}, number={14}, journal={APPLIED PHYSICS LETTERS}, author={Kwon, Seol Ryung and Huang, Wenbin and Shu, Longlong and Yuan, Fuh-Gwo and Maria, Jon-Paul and Jiang, Xiaoning}, year={2014}, month={Oct} }
 @article{atanasov_losego_gong_sachet_maria_williams_parsons_2014, title={Highly Conductive and Conformal Poly(3,4-ethylenedioxythiophene) (PEDOT) Thin Films via Oxidative Molecular Layer Deposition}, volume={26}, ISSN={["1520-5002"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000337199400019&KeyUID=WOS:000337199400019}, DOI={10.1021/cm500825b}, abstractNote={This work introduces oxidative molecular layer deposition (oMLD) as a chemical route to synthesize highly conductive and conformal poly(3,4-ethylenedioxythiophene) (PEDOT) thin films via sequential vapor exposures of molybdenum(V) chloride (MoCl5, oxidant) and ethylene dioxythiophene (EDOT, monomer) precursors. The growth temperature strongly affects PEDOT’s crystalline structure and electronic conductivity. Films deposited at ∼150 °C exhibit a highly textured crystalline structure, with {010} planes aligned parallel with the substrate. Electrical conductivity of these textured films is routinely above 1000 S cm–1, with the most conductive films exceeding 3000 S cm–1. At lower temperatures (∼100 °C) the films exhibit a random polycrystalline structure and display smaller conductivities. Compared with typical electrochemical, solution-based, and chemical vapor deposition techniques, oMLD PEDOT films achieve high conductivity without the need for additives or postdeposition treatments. Moreover, the sequent...}, number={11}, journal={CHEMISTRY OF MATERIALS}, author={Atanasov, Sarah E. and Losego, Mark D. and Gong, Bo and Sachet, Edward and Maria, Jon-Paul and Williams, Philip S. and Parsons, Gregory N.}, year={2014}, month={Jun}, pages={3471–3478} }
 @article{burch_li_garten_sang_lebeau_trolier-mckinstry_maria_dickey_2014, title={Investigation of Local A-site Chemistry in Barium Strontium Titanate Using Aberration Corrected STEM, EELS and EDS}, volume={20}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927614011696}, DOI={10.1017/S1431927614011696}, abstractNote={Barium strontium titante (BST) is an important dielectric material because of its high tunability (dielectric constant as a function of applied voltage) and low loss, with specific applications in tunable microwave circuits. However, regardless of processing technique, additives, or synthesis temperatures some remnant ferroelectricity is always observed beyond the paraelectric phase transition [1]. One possible explanation for this remnant ferroelectricity, which has been hotly debated, is that the local stoichiometry of the A-site cations (Ba and Sr) is not globally and locally homogeneous. This hypothesis surmises that local areas, which are barium rich, may result in remnant polarization [1]. However, this hypothesis has never been experimentally shown. In this work, we use an aberration corrected scanning transmission electron microscope (STEM), electron energy loss spectroscopy (EELS), and energy dispersive X-ray spectroscopy (EDS) to investigate the local stoichiometry of arguably the bestengineered barium strontium titanate samples ever fabricated [2] in comparison to BST thin films showing some of the best tunability in thin-film form.}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Burch, Matthew J. and Li, Jing and Garten, Lauren and Sang, Xiahan and Lebeau, James and Trolier-Mckinstry, Susan and Maria, Jon-Paul and Dickey, Elizabeth C.}, year={2014}, month={Aug}, pages={1992–1993} }
 @article{burch_li_harris_maria_dickey_2014, title={Mechanisms for microstructure enhancement in flux-assisted growth of barium titanate on sapphire}, volume={29}, ISSN={0884-2914 2044-5326}, url={http://dx.doi.org/10.1557/jmr.2014.59}, DOI={10.1557/jmr.2014.59}, abstractNote={Abstract}, number={7}, journal={Journal of Materials Research}, publisher={Cambridge University Press (CUP)}, author={Burch, Matthew J. and Li, Jing and Harris, David T. and Maria, Jon-Paul and Dickey, Elizabeth C.}, year={2014}, month={Mar}, pages={843–848} }
 @article{gaddy_paisley_maria_irving_2014, title={Overcoming the polarization catastrophe in the rocksalt oxides MgO and CaO}, volume={90}, ISSN={["2469-9969"]}, DOI={10.1103/physrevb.90.125403}, abstractNote={Interfaces between dissimilar polar materials may provide a pathway to new device functionality, including high carrier mobility layers at the interface. The development of these materials has proven challenging, in part because of the high energy cost of forming polar surfaces. Our density functional theory calculations explore the mechanisms by which a real material satisfies the electrostatic criteria for stability imposed by a polar surface. The consequences of polarity are studied by comparing the formation energies, charge distribution, and electronic structure of a number of low-index surfaces of rocksalt MgO and CaO. These surfaces are explored both in their bare, undecorated form as well as with surface reconstructions and adsorbed foreign species. Our ground-state surface energies are extended to relevant environmental conditions by use of ab initio thermodynamics. We find that the high energy of bare polar surfaces is the result of the significant charge redistribution that arises to compensate the polarity and pushes electronic states into the forbidden band gap. Other mechanisms of polarity compensation (reconstruction or foreign species adsorption) are therefore seen more frequently. We explain the experimental observations of surface roughness during growth in the [111] direction. In typical epitaxial growth conditions, there is preferential formation of an octopolar reconstruction of the {111} surface, which exposes {001}-type nanofacets. The low energy of the {001} surface likely causes these facets to grow, leading to a rough surface morphology. Our results indicate that when water vapor is present during growth, a smooth, polar surface can be stabilized by the formation of a hydroxyl layer.}, number={12}, journal={PHYSICAL REVIEW B}, author={Gaddy, Benjamin E. and Paisley, Elizabeth A. and Maria, Jon-Paul and Irving, Douglas L.}, year={2014}, month={Sep} }
 @article{oni_hook_maria_lebeau_2014, title={Phase coexistence in Ti6Sn5 intermetallics}, volume={51}, ISSN={["1879-0216"]}, DOI={10.1016/j.intermet.2014.03.002}, abstractNote={Here we report the structural characterization of a complex Ti–Sn intermetallic compound, Ti6Sn5. From X-ray diffraction, the resulting compound was observed to exist in both orthorhombic and hexagonal phases. Analysis by electron microscopy revealed that “planar-like” defects form throughout the material. Atomic resolution aberration-corrected scanning transmission electron microscopy reveals that these “planar-like” defects represent the coexistence of the orthorhombic and hexagonal phases within single grains. The resulting interwoven phases range in thickness from a fraction to multiple unit cells and exhibit coherent phase boundaries with the matrix grain.}, journal={INTERMETALLICS}, author={Oni, A. A. and Hook, D. and Maria, J. P. and LeBeau, J. M.}, year={2014}, month={Aug}, pages={48–52} }
 @article{shelton_sachet_paisley_hoffmann_rajan_collazo_sitar_maria_2014, title={Polarity characterization by anomalous x-ray dispersion of ZnO films and GaN lateral polar structures}, volume={115}, ISSN={["1089-7550"]}, DOI={10.1063/1.4863120}, abstractNote={We demonstrate the use of anomalous x-ray scattering of constituent cations at their absorption edge, in a conventional Bragg-Brentano diffractometer, to measure absolutely and quantitatively the polar orientation and polarity fraction of unipolar and mixed polar wurtzitic crystals. In one set of experiments, the gradual transition between c+ and c− polarity of epitaxial ZnO films on sapphire as a function of MgO buffer layer thickness is monitored quantitatively, while in a second experiment, we map the polarity of a lateral polar homojunction in GaN. The dispersion measurements are compared with piezoforce microscopy images, and we demonstrate how x-ray dispersion and scanning probe methods can provide complementary information that can discriminate between polarity fractions at a material surface and polarity fractions averaged over the film bulk.}, number={4}, journal={JOURNAL OF APPLIED PHYSICS}, author={Shelton, Christopher T. and Sachet, Edward and Paisley, Elizabeth A. and Hoffmann, Marc P. and Rajan, Joseph and Collazo, Ramon and Sitar, Zlatko and Maria, Jon-Paul}, year={2014}, month={Jan} }
 @article{garten_lam_harris_maria_trolier-mckinstry_2014, title={Residual ferroelectricity in barium strontium titanate thin film tunable dielectrics}, volume={116}, DOI={10.1063/1.4891717}, abstractNote={Loss reduction is critical to develop Ba1−xSrxTiO3 thin film tunable microwave dielectric components and dielectric energy storage devices. The presence of ferroelectricity, and hence the domain wall contributions to dielectric loss, will degrade the tunable performance in the microwave region. In this work, residual ferroelectricity—a persistent ferroelectric response above the global phase transition temperature—was characterized in tunable dielectrics using Rayleigh analysis. Chemical solution deposited Ba0.7Sr0.3TiO3 films, with relative tunabilities of 86% over 250 kV/cm at 100 kHz, demonstrated residual ferroelectricity 65 °C above the ostensible paraelectric transition temperature. Frequency dispersion observed in the dielectric temperature response was consistent with the presence of nanopolar regions as one source of residual ferroelectricity. The application of AC electric field for the Rayleigh analysis of these samples led to a doubling of the dielectric loss for fields over 10 kV/cm at room temperature.}, number={4}, journal={Journal of Applied Physics}, author={Garten, L. M. and Lam, P. and Harris, D. and Maria, J. P. and Trolier-McKinstry, S.}, year={2014} }
 @article{paisley_gaddy_lebeau_shelton_biegalski_christen_losego_mita_collazo_sitar_et al._2014, title={Smooth cubic commensurate oxides on gallium nitride}, volume={115}, ISSN={["1089-7550"]}, DOI={10.1063/1.4861172}, abstractNote={Smooth, commensurate alloys of ⟨111⟩-oriented Mg0.52Ca0.48O (MCO) thin films are demonstrated on Ga-polar, c+ [0001]-oriented GaN by surfactant-assisted molecular beam epitaxy and pulsed laser deposition. These are unique examples of coherent cubic oxide|nitride interfaces with structural and morphological perfection. Metal-insulator-semiconductor capacitor structures were fabricated on n-type GaN. A comparison of leakage current density for conventional and surfactant-assisted growth reveals a nearly 100× reduction in leakage current density for the surfactant-assisted samples. HAADF-STEM images of the MCO|GaN interface show commensurate alignment of atomic planes with minimal defects due to lattice mismatch. STEM and DFT calculations show that GaN c/2 steps create incoherent boundaries in MCO over layers which manifest as two in-plane rotations and determine consequently the density of structural defects in otherwise coherent MCO. This new understanding of interfacial steps between HCP and FCC crystals identifies the steps needed to create globally defect-free heterostructures.}, number={6}, journal={JOURNAL OF APPLIED PHYSICS}, author={Paisley, Elizabeth A. and Gaddy, Benjamin E. and LeBeau, James M. and Shelton, Christopher T. and Biegalski, Michael D. and Christen, Hans M. and Losego, Mark D. and Mita, Seiji and Collazo, Ramon and Sitar, Zlatko and et al.}, year={2014}, month={Feb} }
 @article{donovan_foley_ihlefeld_maria_hopkins_2014, title={Spectral phonon scattering effects on the thermal conductivity of nano-grained barium titanate}, volume={105}, ISSN={["1077-3118"]}, DOI={10.1063/1.4893920}, abstractNote={We study the effect of grain size on thermal conductivity of thin film barium titanate over temperatures ranging from 200 to 500 K. We show that the thermal conductivity of Barium Titanate (BaTiO3) decreases with decreasing grain size as a result of increased phonon scattering from grain boundaries. We analyze our results with a model for thermal conductivity that incorporates a spectrum of mean free paths in BaTiO3. In contrast to the common gray mean free path assumption, our findings suggest that the thermal conductivity of complex oxide perovskites is driven by a spectrum of phonons with varying mean free paths.}, number={8}, journal={APPLIED PHYSICS LETTERS}, author={Donovan, Brian F. and Foley, Brian M. and Ihlefeld, Jon F. and Maria, Jon-Paul and Hopkins, Patrick E.}, year={2014}, month={Aug} }
 @article{faraji_stano_rost_maria_zhu_bradford_2014, title={Structural annealing of carbon coated aligned multi-walled carbon nanotube sheets}, volume={79}, ISSN={0008-6223}, url={http://dx.doi.org/10.1016/J.CARBON.2014.07.049}, DOI={10.1016/j.carbon.2014.07.049}, abstractNote={Sheets of aligned multi-walled carbon nanotubes (AMWCNTs) were used to study the structural annealing of pyrolytic carbon (PyC) coatings with various thicknesses on MWCNTs. PyC was deposited using chemical vapor infiltration and the thickness was controlled via the infiltration time. Structural annealing of the PyC coated AMWCNT (AMWCNT/C) sheets at 2150 °C provided different results for different thickness coatings. Transmission electron microscopy images showed that the carbon deposited from acetylene formed laminar PyC coatings, resembling rough tube walls, on the CNT surfaces. Following the high temperature heat treatment, coatings from short PyC deposition times changed their structure, resulting in radial growth of the MWCNTs. Raman and X-ray diffraction measurements also revealed that the radially grown MWCNTs had graphitic quality very close to pristine nanotubes after annealing. Electrical conductivity of AMWCNT/C sheets after high temperature heat treatment was twice that of pristine AMWCNT sheets. The focus of this study was to determine the PyC coating thickness at which a rough PyC coating would no longer change its structure into new CNT walls. The samples treated longer than 30 min had much more disordered PyC deposited on the surface and the additional material did not form additional tube walls after thermal annealing.}, journal={Carbon}, publisher={Elsevier BV}, author={Faraji, Shaghayegh and Stano, Kelly and Rost, Christina and Maria, Jon-Paul and Zhu, Yuntian and Bradford, Philip D.}, year={2014}, month={Nov}, pages={113–122} }
 @article{mily_oni_lebeau_liu_brown-shaklee_ihlefeld_maria_2014, title={The role of terminal oxide structure and properties in nanothermite reactions}, volume={562}, ISSN={["0040-6090"]}, DOI={10.1016/j.tsf.2014.05.005}, journal={THIN SOLID FILMS}, author={Mily, E. J. and Oni, A. and LeBeau, J. M. and Liu, Y. and Brown-Shaklee, H. J. and Ihlefeld, J. F. and Maria, J. -P.}, year={2014}, month={Jul}, pages={405–410} }
 @article{harris_lam_burch_li_rogers_dickey_maria_2014, title={Ultra-high tunability in polycrystalline Ba1−xSrxTiO3 thin films}, volume={105}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4893615}, DOI={10.1063/1.4893615}, abstractNote={Ba0.7Sr0.3TiO3 thin polycrystalline films with an ultra-high capacitance tunability approaching 5:1 at 175 kV/cm were made possible by a flux-assisted synthesis approach. In this process, a small volume fraction of a low melting temperature glass is added during low-temperature sputter deposition. Subsequent annealing activates the liquid phase, which in turn provides the mass transport needed to approach full density, to increase grain size, and to improve crystallinity, and, in so doing, achieves a stronger non-linear dielectric response. Ba0.7Sr0.3TiO3 films with 0%, 1%, 4%, and 7% BaO-3B2O3 flux exhibited grain sizes of 25 nm, 28 nm, 48 nm, and 56 nm, and dielectric tunabilities of 25%, 33%, 64%, and 80% respectively. These values represent substantial improvements when compared to conventionally processed tunable dielectric films.}, number={7}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Harris, D. T. and Lam, P. G. and Burch, M. J. and Li, J. and Rogers, B. J. and Dickey, E. C. and Maria, J.-P.}, year={2014}, month={Aug}, pages={072904} }
 @article{paisley_craft_losego_lu_gruverman_collazo_sitar_maria_2013, title={Epitaxial PbxZr1-xTiO3 on GaN}, volume={113}, ISSN={["1089-7550"]}, DOI={10.1063/1.4792599}, abstractNote={Epitaxial integration of PbxZr1−xTiO3 (PZT) (111) with GaN (0002) presents the possibility of polarity coupling across a functional-oxide/nitride heteropolar interface. This work describes the synthesis and characterization of such thin film heterostructures by magnetron sputtering, with specific attention given to process optimization. Using x-ray diffraction and electrical characterization, the growth of epitaxial PZT (∼250 nm) on GaN and PZT on MgO/GaN stacks was verified. A two-stage growth process was developed for epitaxial PZT with a deposition temperature of 300 °C and an ex-situ anneal at 650 °C, which was effective in mitigating interfacial reactions and promoting phase-pure perovskite growth. Electrical analysis of interdigital capacitors revealed a nonlinear and hysteretic dielectric response consistent with ferroelectric PZT. Piezoresponse force microscopy (PFM) characterization shows clear evidence of ferroelectric switching, and PFM hysteresis loop analysis shows minimal evidence for direct polarity coupling, but suggests that band offsets which accompany the oxide-nitride heterostructures influence switching.}, number={7}, journal={JOURNAL OF APPLIED PHYSICS}, author={Paisley, E. A. and Craft, H. S. and Losego, M. D. and Lu, H. and Gruverman, A. and Collazo, R. and Sitar, Z. and Maria, J. -P.}, year={2013}, month={Feb} }
 @article{paisley_craft_losego_lu_gruverman_collazo_sitar_maria_2013, title={Epitaxial lead zirconate titanate on gallium nitride (vol 113, 074107, 2013)}, volume={114}, number={23}, journal={Journal of Applied Physics}, author={Paisley, E. A. and Craft, H. S. and Losego, M. D. and Lu, H. and Gruverman, A. and Collazo, R. and Sitar, Z. and Maria, J. P.}, year={2013} }
 @article{estrich_hook_smith_leonard_laughlin_maria_2013, title={Ga-doped ZnO conducting antireflection coatings for crystalline silicon solar cells}, volume={113}, ISSN={["0021-8979"]}, DOI={10.1063/1.4811538}, abstractNote={Transparent, conductive gallium-doped ZnO thin films are evaluated for application as conducting antireflection coatings (ARC) for crystalline silicon solar cells as a means to enhance efficiency by reducing the overall resistivity of the photovoltaic circuit. All Ga-doped ZnO thin films in this study were deposited using pulsed laser deposition. Synthesis conditions were first optimized for maximum electrical resistivity and minimal visible light absorption. The ideal combination contained 1 mol. % Ga doping and exhibited ∼90% transmission, with resistivity in the 1 × 10−3 ohm-cm range. Optimized films were prepared on reference flat silicon wafers with known dopant densities and on commercially obtained solar cell emitters without ARCs. Circular transmission line method measurements were used to measure specific contact resistivity (ρc). For n-type doped solar cell emitters, contact resistivity values of 0.1 mΩ cm2 were observed repeatedly. These values are consistent with, or lower than, contact resistivities associated with conventional silver paste metallization.}, number={23}, journal={JOURNAL OF APPLIED PHYSICS}, author={Estrich, N. A. and Hook, D. H. and Smith, A. N. and Leonard, J. T. and Laughlin, B. and Maria, J. -P.}, year={2013}, month={Jun} }
 @article{kirste_hoffmann_sachet_bobea_bryan_bryan_nenstiel_hoffmann_maria_collazo_et al._2013, title={Ge doped GaN with controllable high carrier concentration for plasmonic applications}, volume={103}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4848555}, DOI={10.1063/1.4848555}, abstractNote={Controllable Ge doping in GaN is demonstrated for carrier concentrations of up to 2.4 × 1020 cm−3. Low temperature luminescence spectra from the highly doped samples reveal band gap renormalization and band filling (Burstein-Moss shift) in addition to a sharp transition. Infrared ellipsometry spectra demonstrate the existence of electron plasma with an energy around 3500 cm−1 and a surface plasma with an energy around 2000 cm−1. These findings open possibilities for the application of highly doped GaN for plasmonic devices.}, number={24}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Kirste, Ronny and Hoffmann, Marc P. and Sachet, Edward and Bobea, Milena and Bryan, Zachary and Bryan, Isaac and Nenstiel, Christian and Hoffmann, Axel and Maria, Jon-Paul and Collazo, Ramón and et al.}, year={2013}, month={Dec}, pages={242107} }
 @article{li_burch_harris_maria_dickey_2013, title={Interface Evolution of Flux-Grown BaTiO3 Thin Films on Sapphire Substrates}, volume={19}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927613011422}, DOI={10.1017/S1431927613011422}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.}, number={S2}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Li, J. and Burch, M. and Harris, D.T. and Maria, J.-P. and Dickey, E.C.}, year={2013}, month={Aug}, pages={1886–1887} }
 @article{rao_prater_wu_shelton_maria_narayan_2013, title={Interface Magnetism in Epitaxial BiFeO3-La0.7Sr0.3MnO3 Heterostructures Integrated on Si(100)}, volume={13}, ISSN={["1530-6992"]}, DOI={10.1021/nl4023435}, abstractNote={We report on the heteroepitaxial growth of ferroelectric (FE)-antiferromagnetic (AFM) BiFeO3 (BFO) on ferromagnetic La0.7Sr0.3MnO3 (LSMO), integrated on Si(100) using pulsed laser deposition via the domain matching epitaxy paradigm. The BFO/LSMO films were epitaxially grown on Si(100) by introducing epitaxial layers of SrTiO3/MgO/TiN. X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photo absorption spectroscopy, and atomic force microscopy were employed to fully characterize the samples. Furthermore, we have investigated the magnetic behavior of this five layer heterostructure, in which a d(5) system (Fe(3+)) manifested in FE-AFM BFO is epitaxially conjoined at the interface to a multivalent transition metal ion such as Mn(3+)/Mn(4+) in LSMO. The temperature- and magnetic field-dependent magnetization measurements reveal an unexpected enhancement in magnetic moment and improved magnetic hysteresis squareness originating from the BFO/LSMO interface. We observe a stronger temperature dependence of HEB when the polarity of field cooling is negative as compared to positive field cooling. We believe such an enhancement in magnetic moment and magnetic coupling is likely directly related to an electronic orbital reconstruction at the interface and complex interplay between orbital and spin degrees of freedom, similar to what has previously been reported in the literature. Future work will involve the linearly polarized X-ray absorption measurements to prove this hypothesis. This work represents a starting step toward the realization of magneto-electronic devices integrated with Si(100).}, number={12}, journal={NANO LETTERS}, author={Rao, S. S. and Prater, J. T. and Wu, Fan and Shelton, C. T. and Maria, J. -P. and Narayan, J.}, year={2013}, month={Dec}, pages={5814–5821} }
 @article{sachet_losego_guske_franzen_maria_2013, title={Mid-infrared surface plasmon resonance in zinc oxide semiconductor thin films}, volume={102}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4791700}, DOI={10.1063/1.4791700}, abstractNote={Surface plasmon resonance (SPR) in semiconducting materials at mid-infrared (mid-IR) energies offers the potential for new plasmonic functionalities and integration schemes. Mainstream semiconductors are transparent to mid-IR energies, thus a tightly integrated monolithic package for SPR sensing becomes feasible. We report mid-IR surface plasmon resonance in zinc oxide as a model material for semiconductors with 4 × 1019 to 8 × 1019 cm−3 carriers. The surface plasmon modes were characterized using spectroscopic IR-ellipsometry and compared to a reflectivity simulation. The data confirm the feasibility of mid-IR SPR, show a generic ability for plasmon tuning, and demonstrate the predictive power of the reflectivity model.}, number={5}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Sachet, Edward and Losego, Mark D. and Guske, Joshua and Franzen, Stefan and Maria, Jon-Paul}, year={2013}, month={Feb}, pages={051111} }
 @article{casper_losego_maria_2013, title={Optimizing phase and microstructure of chemical solution-deposited bismuth ferrite (BiFeO3) thin films to reduce DC leakage}, volume={48}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-012-6914-0}, number={4}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Casper, Michelle D. and Losego, Mark D. and Maria, Jon-Paul}, year={2013}, month={Feb}, pages={1578–1584} }
 @article{paisley_craft_losego_lu_gruverman_collazo_sitar_maria_2013, title={Publisher's Note: “Epitaxial lead zirconate titanate on gallium nitride” [J. Appl. Phys. 113, 074107 (2013)]}, volume={114}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.4842135}, DOI={10.1063/1.4842135}, number={23}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Paisley, E. A. and Craft, H. S. and Losego, M. D. and Lu, H. and Gruverman, A. and Collazo, R. and Sitar, Z. and Maria, J.-P.}, year={2013}, month={Dec}, pages={239901} }
 @article{harris_burch_ihlefeld_lam_li_dickey_maria_2013, title={Realizing strain enhanced dielectric properties in BaTiO3 films by liquid phase assisted growth}, volume={103}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4813270}, DOI={10.1063/1.4813270}, abstractNote={The addition of a liquid-forming flux to barium titanate thin films promotes densification and grain growth, improves nonlinear dielectric properties, and allows residual strain to be sustained in polycrystalline films without cracking at thicknesses relevant to device fabrication. Relative tuning, an excellent indicator of crystalline quality and an important material property for tunable microwave devices, increases from 20% to 70%. Films exhibit 0.15% residual differential thermal expansion mismatch strain, resulting in a shift to the paraelectric-ferroelectric phase transition of 50 °C. This result is in excellent agreement with theory, demonstrating the ability to tune ferroic transitions without epitaxial approaches.}, number={1}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Harris, David T. and Burch, Matthew J. and Ihlefeld, Jon F. and Lam, Peter G. and Li, Jing and Dickey, Elizabeth C. and Maria, Jon-Paul}, year={2013}, month={Jul}, pages={012904} }
 @article{stuart_satchet_sandin_maria_rowe_dougherty_ulrich_2013, title={Smooth MgO films grown on graphite and graphene by pulsed laser deposition}, volume={31}, ISSN={["2166-2746"]}, DOI={10.1116/1.4818511}, abstractNote={Pulsed laser deposition was used to grow thin (1–100 nm) magnesium oxide films directly on graphite and epitaxial graphene on SiC(0001). The authors observe very smooth (typical rms roughness of ∼0.4 nm) film morphologies that are nearly independent of film thickness and conformal to the substrate for films grown on room temperature substrates. Surface roughness is less than 1 nm for thicknesses up to 100 nm and is independent of oxygen background pressure during growth. X-ray diffraction shows no evidence of crystallinity for films grown on room temperature substrates but shows ⟨100⟩ texture for films grown on heated substrates that also have very rough surface morphologies. X-ray photoelectron spectroscopy shows hydroxylation of films due to air exposure that can only be partially removed by annealing, indicating the presence of atomic defects in the films.}, number={5}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Stuart, Sean C. and Satchet, Edward and Sandin, Andreas and Maria, Jon-Paul and Rowe, John E. and Dougherty, Daniel B. and Ulrich, Marc}, year={2013}, month={Sep} }
 @article{casper_gözen_dickey_genzer_maria_2013, title={Surface wrinkling by chemical modification of poly(dimethylsiloxane)-based networks during sputtering}, volume={9}, ISSN={1744-683X 1744-6848}, url={http://dx.doi.org/10.1039/C3SM50966D}, DOI={10.1039/c3sm50966d}, abstractNote={Wrinkling is an important mechanical phenomenon that generates periodic topographical patterns across a surface. This paper presents experimental evidence that surface wrinkles, which form consequent to thin film magnetron sputtering of either indium tin oxide (ITO) or aluminum on poly(dimethylsiloxane) networks (PDMS-N) made from a commercial Sylgard-184 kit, result from chemical modification of the PDMS-N surface as opposed to extrinsic thermomechanical stresses originating from differential thermal expansion. X-ray photoelectron spectroscopy results reveal that the PDMS-N surface becomes depleted in carbon and concurrently enriched in oxygen relative to silicon due to sputtering. This silica-like surface layer possesses intrinsic compressive stress that leads to wrinkle formation during the first ≈5 seconds of sputtering. The wrinkles maintain their periodicity irrespective of the thickness of the ITO film formed during subsequent deposition. Furthermore, upon removal of the ITO layer, the wrinkles persist with their periodicity unchanged. A narrow sputtering pressure window between 2 and 12 mTorr generates wrinkles. Pressures below this range cannot sustain a radio frequency plasma, while pressures above this range provide sufficient thermalization of kinetic energy as to eliminate the energetic bombardment that modifies the PDMS-N. This study provides a new understanding of the origins of wrinkling in sputtered films on polymeric substrates and creates opportunities to manipulate the topography produced by spontaneous surface wrinkling.}, number={32}, journal={Soft Matter}, publisher={Royal Society of Chemistry (RSC)}, author={Casper, Michelle D. and Gözen, Arif Ö. and Dickey, Michael D. and Genzer, Jan and Maria, Jon-Paul}, year={2013}, pages={7797} }
 @misc{rohrer_affatigato_backhaus_bordia_chan_curtarolo_demkov_eckstein_faber_garay_et al._2012, title={Challenges in Ceramic Science: A Report from the Workshop on Emerging Research Areas in Ceramic Science}, volume={95}, ISSN={["1551-2916"]}, DOI={10.1111/jace.12033}, abstractNote={In March 2012, a group of researchers met to discuss emerging topics in ceramic science and to identify grand challenges in the field. By the end of the workshop, the group reached a consensus on eight challenges for the future:—understanding rare events in ceramic microstructures, understanding the phase‐like behavior of interfaces, predicting and controlling heterogeneous microstructures with unprecedented functionalities, controlling the properties of oxide electronics, understanding defects in the vicinity of interfaces, controlling ceramics far from equilibrium, accelerating the development of new ceramic materials, and harnessing order within disorder in glasses. This paper reports the outcomes of the workshop and provides descriptions of these challenges.}, number={12}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Rohrer, Gregory S. and Affatigato, Mario and Backhaus, Monika and Bordia, Rajendra K. and Chan, Helen M. and Curtarolo, Stefano and Demkov, Alex and Eckstein, James N. and Faber, Katherine T. and Garay, Javier E. and et al.}, year={2012}, month={Dec}, pages={3699–3712} }
 @article{shelton_kotula_brennecka_lam_meyer_maria_gibbons_ihlefeld_2012, title={Chemically Homogeneous Complex Oxide Thin Films Via Improved Substrate Metallization}, volume={22}, ISSN={["1616-301X"]}, DOI={10.1002/adfm.201103077}, abstractNote={Abstract}, number={11}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Shelton, Christopher T. and Kotula, Paul G. and Brennecka, Geoff L. and Lam, Peter G. and Meyer, Kelsey E. and Maria, Jon-Paul and Gibbons, Brady J. and Ihlefeld, Jon F.}, year={2012}, month={Jun}, pages={2295–2302} }
 @article{shelton_kotula_brennecka_lam_meyer_maria_gibbons_ihlefeld_2012, title={Functional Coatings: Chemically Homogeneous Complex Oxide Thin Films Via Improved Substrate Metallization (Adv. Funct. Mater. 11/2012)}, volume={22}, ISSN={1616-301X}, url={http://dx.doi.org/10.1002/adfm.201290066}, DOI={10.1002/adfm.201290066}, abstractNote={On page 2295, Jon F. Ihlefeld and co-workers reveal how proper metallization adhesion layer selection results in chemically homogeneous complex oxide films with enhanced ferroelectric and dielectric responses. The image shows a cross-sectional scanning electron microscopy image of a lead zircon ate titanate thin film on a platinized silicon wafer.}, number={11}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Shelton, Christopher T. and Kotula, Paul G. and Brennecka, Geoff L. and Lam, Peter G. and Meyer, Kelsey E. and Maria, Jon-Paul and Gibbons, Brady J. and Ihlefeld, Jon F.}, year={2012}, month={Jun}, pages={2214–2214} }
 @article{burch_harris_white_moballegh_li_maria_dickey_2012, title={In situ heating studies of flux grown barium titanate thin films}, volume={18}, url={https://app.dimensions.ai/details/publication/pub.1054927598}, DOI={10.1017/s1431927612009245}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.}, number={S2}, journal={Microscopy and Microanalysis}, author={Burch, M.J. and Harris, D. and White, R.M. and Moballegh, A. and Li, J. and Maria, J.P. and Dickey, Elizabeth C.}, year={2012}, pages={1478–1479} }
 @article{lam_haridasan_feng_steer_kingon_maria_2012, title={Scaling Issues in Ferroelectric Barium Strontium Titanate Tunable Planar Capacitors}, volume={59}, ISSN={["1525-8955"]}, DOI={10.1109/tuffc.2012.2179}, abstractNote={We report on the geometric limits associated with tunability of interdigitated capacitors, specifically regarding the impact of a parasitic non-tunable component that necessarily accompanies a ferroelectric surface capacitor, and can dominate the voltage-dependent response as capacitor dimensions are reduced to achieve the small capacitance values required for impedance matching in the X band. We present a case study of simple gap capacitors prepared and characterized as a function of gap width (i.e., the distance between electrodes) and gap length (i.e., the edge-to-edge gap distance). Our series of measurements reveals that for gap widths in the micrometer range, as gap lengths are reduced to meet sub-picofarad capacitance values, the non-tunable parasitic elements limit the effective tunability. These experimental measurements are supported by a companion set of microwave models that clarify the existence of parallel parasitic elements.}, number={2}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, author={Lam, Peter G. and Haridasan, Vrinda and Feng, Zhiping and Steer, Michael B. and Kingon, Angus I. and Maria, Jon-Paul}, year={2012}, month={Feb}, pages={198–204} }
 @article{seifikar_calandro_deeb_sachet_yang_maria_bassiri-gharb_schwartz_2012, title={Structural and magnetic properties of biaxially textured NiFe2O4 thin films grown on c-plane sapphire}, volume={112}, ISSN={["1089-7550"]}, DOI={10.1063/1.4770366}, abstractNote={Chemical solution deposition is used to grow biaxially textured NiFe2O4 (NFO) thin films on (0001) sapphire substrates; a high degree of out-of-plane orientation in the 〈111〉 direction is confirmed by θ–2θ X-ray diffraction and pole figures. X-ray φ-scanning indicates in-plane texture and an epitaxial relationship between NFO (111) and Al2O3 (0001) in two crystallographic variants. The out-of-plane magnetization exhibits improved Mr/Ms from 0.5 in 110 nm-thick films to 0.8 in 60 nm-thick films. Compared to uniaxially textured NFO films on platinized silicon, the out-of-plane coercivity is reduced by 20%. The improved out-of-plane magnetic anisotropy is comparable to epitaxial NFO films of similar thickness deposited by pulsed laser deposition and sputtering.}, number={12}, journal={JOURNAL OF APPLIED PHYSICS}, author={Seifikar, Safoura and Calandro, Bridget and Deeb, Elisabeth and Sachet, Edward and Yang, Jijin and Maria, Jon-Paul and Bassiri-Gharb, Nazanin and Schwartz, Justin}, year={2012}, month={Dec} }
 @article{paisley_shelton_mita_collazo_christen_sitar_biegalski_maria_2012, title={Surfactant assisted growth of MgO films on GaN}, volume={101}, ISSN={["0003-6951"]}, DOI={10.1063/1.4748886}, abstractNote={Thin epitaxial films of 〈111〉 oriented MgO on [0001]-oriented GaN were grown by molecular beam epitaxy and pulsed laser deposition using the assistance of a vapor phase surfactant. In both cases, surfactant incorporation enabled layer-by-layer growth and a smooth terminal surface by stabilizing the {111} rocksalt facet. Metal-insulator-semiconductor capacitor structures were fabricated on n-type GaN. A comparison of leakage current density for conventional and surfactant-assisted growth reveals a nearly 100× reduction in leakage current density for the surfactant-assisted samples. These data verify numerous predictions regarding the role of H-termination in regulating the habit of rocksalt crystals.}, number={9}, journal={APPLIED PHYSICS LETTERS}, author={Paisley, E. A. and Shelton, T. C. and Mita, S. and Collazo, R. and Christen, H. M. and Sitar, Z. and Biegalski, M. D. and Maria, J. -P.}, year={2012}, month={Aug} }
 @article{losego_guske_efremenko_maria_franzen_2011, title={Characterizing the Molecular Order of Phosphonic Acid Self-Assembled Monolayers on Indium Tin Oxide Surfaces}, volume={27}, ISSN={["0743-7463"]}, DOI={10.1021/la201161q}, abstractNote={Self-assembled monolayers (SAMs) of alkanephosphonic acids with chain lengths between 8 and 18 carbon units were formed on thin films of indium tin oxide (ITO) sputter-deposited on silicon substrates with 400 nm thermally grown SiO(2). The silicon substrates, while not intended for use in near-IR or visible optics applications, do provide smooth surfaces that permit systematic engineering of grain size and surface roughness as a function of the sputter pressure. Argon sputter pressures from 4 to 20 mTorr show systematic changes in surface morphology ranging from smooth, micrometer-sized grain structures to <50 nm grains with 3× higher surface roughness. Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy experiments are conducted for alkanephosphonic acids deposited on these wide range of ITO surfaces to evaluate the effects of these morphological features on monolayer ordering. Results indicate that long-chain SAMs are more highly ordered, and have a smaller tilt angle, than short-chain SAMs. Surprisingly, the 1-octadecyl phosphonic acids maintain their order as the lateral grain dimensions of the ITO surface shrink to ∼50 nm. It is only when the ITO surface roughness becomes greater than the SAM chain length (∼15 Å) that SAMs are observed to become relatively disordered.}, number={19}, journal={LANGMUIR}, author={Losego, Mark D. and Guske, Joshua T. and Efremenko, Alina and Maria, Jon-Paul and Franzen, Stefan}, year={2011}, month={Oct}, pages={11883–11888} }
 @article{jur_wheeler_lichtenwalner_maria_johnson_2011, title={Epitaxial growth of lanthanide oxides La2O3 and Sc2O3 on GaN}, volume={98}, ISSN={["0003-6951"]}, DOI={10.1063/1.3541883}, abstractNote={Deposition of lanthanide oxides on GaN is investigated as a means to produce stable dielectric with good interface quality. Epitaxial growth of cubic ⟨111⟩-oriented Sc2O3 is observed on GaN [0001] with a lattice mismatch of 7.2%, whereas La2O3 growth, with a lattice mismatch of ∼21%, results in a mixed phase epitaxial film comprised of the bixbyite and hexagonal allotropes. Substantial roughening accompanies this mixed phase film. By inserting a thin Sc2O3 interfacial layer between La2O3 and GaN and a Sc2O3 capping layer, the crystal quality of the predominantly La2O3 layer is improved and the stack is stabilized against hydroxide formation under ambient conditions.}, number={4}, journal={APPLIED PHYSICS LETTERS}, author={Jur, Jesse S. and Wheeler, Virginia D. and Lichtenwalner, Daniel J. and Maria, Jon-Paul and Johnson, Mark A. L.}, year={2011}, month={Jan} }
 @article{akyildiz_casper_ayguen_lam_maria_2011, title={Hydrothermal BaTiO3 thin films from nanostructured Ti templates}, volume={26}, ISSN={["0884-2914"]}, DOI={10.1557/jmr.2010.102}, abstractNote={Abstract}, number={4}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Akyildiz, Hasan and Casper, Michelle D. and Ayguen, Seymen M. and Lam, Peter G. and Maria, Jon P.}, year={2011}, month={Feb}, pages={592–599} }
 @article{wang_bradford_liu_zhao_inoue_maria_li_yuan_zhu_2011, title={Mechanical and electrical property improvement in CNT/Nylon composites through drawing and stretching}, volume={71}, ISSN={["1879-1050"]}, DOI={10.1016/j.compscitech.2011.07.023}, abstractNote={The excellent mechanical properties of carbon nanotubes (CNTs) make them the ideal reinforcements for high performance composites. The misalignment and waviness of CNTs within composites are two major issues that limit the reinforcing efficiency. We report an effective method to increase the strength and stiffness of high volume fraction, aligned CNT composites by reducing CNT waviness using a drawing and stretching approach. Stretching the composites after fabrication improved the ultimate strength by 50%, 150%, and 190% corresponding to stretch ratios of 2%, 4% and 7%, respectively. Improvement of the electrical conductivities exhibited a similar trend. These results demonstrate the importance of straightening and aligning CNTs in improving the composite strength and electrical conductivity.}, number={14}, journal={COMPOSITES SCIENCE AND TECHNOLOGY}, author={Wang, Xin and Bradford, Philip D. and Liu, Wei and Zhao, Haibo and Inoue, Yoku and Maria, Jon-Paul and Li, Qingwen and Yuan, Fuh-Gwo and Zhu, Yuntian}, year={2011}, month={Sep}, pages={1677–1683} }
 @article{ayguen_ihlefeld_borland_maria_2011, title={Permittivity scaling in Ba1-xSrxTiO3 thin films and ceramics}, volume={109}, ISSN={["1089-7550"]}, DOI={10.1063/1.3514127}, abstractNote={A dramatic enhancement in the electromechanical response of barium titanate thin films is demonstrated by understanding and optimizing the relationship between organic removal, crystallization, and microstructure, which therefore results in pore elimination, larger grain sizes, and superior densification. The combination enables one to produce bulk-like dielectric properties in a thin film with a room temperature permittivity value above 3000. This advancement in complex oxide thin film processing science creates a new perspective from which to compare, parameterize, and better understand a collection of literature data concerning the manner in which the dielectric response of BaTiO3 depends upon physical dimensions. We are consequently able to apply a single physical model to bulk ceramic and thin film systems, and so demonstrate that the existence of parasitic interfacial layers are not needed to explain dielectric scaling. This work is instrumental in illustrating that extrinsic contributions to scaling are predominant, and that a fundamental understanding of material synthesis provides important opportunities to broaden the spectrum of nonlinear electromechanical properties that can be achieved in ferroelectric thin films.}, number={3}, journal={JOURNAL OF APPLIED PHYSICS}, author={Ayguen, Seymen M. and Ihlefeld, Jon F. and Borland, William J. and Maria, Jon-Paul}, year={2011}, month={Feb} }
 @article{craft_rice_collazo_sitar_maria_2011, title={Spectroscopic measurements of the surface stoichiometry of chemical vapor deposited GaN}, volume={98}, ISSN={["0003-6951"]}, DOI={10.1063/1.3554762}, abstractNote={We report on the surface stoichiometry of Ga-polar GaN films grown by metalorganic chemical vapor deposition as studied by x-ray photoelectron spectroscopy. GaN film surfaces are found to be Ga-rich, with Ga:N ratios ranging from 1.3:1 to 3.2:1. In vacuo ion-beam sputter/annealing studies show that these treatments drive the apparent Ga:N surface composition farther from unity, either through a decrease in surface contamination, oxidation of the surface, or both. Simple annealing experiments decrease the Ga:N ratio. The measured GaN ratio is correlated with the GaN growth time, suggesting that residual Ga precursor after growth interacts with the GaN surface as it cools.}, number={8}, journal={APPLIED PHYSICS LETTERS}, author={Craft, H. S. and Rice, A. L. and Collazo, R. and Sitar, Z. and Maria, J. -P.}, year={2011}, month={Feb} }
 @article{paisley_losego_gaddy_tweedie_collazo_sitar_irving_maria_2011, title={Surfactant-enabled epitaxy through control of growth mode with chemical boundary conditions}, volume={2}, ISSN={["2041-1723"]}, DOI={10.1038/ncomms1470}, abstractNote={Property coupling at interfaces between active materials is a rich source of functionality, if defect densities are low, interfaces are smooth and the microstructure is featureless. Conventional synthesis techniques generally fail to achieve this when materials have highly dissimilar structure, symmetry and bond type-precisely when the potential for property engineering is most pronounced. Here we present a general synthesis methodology, involving systematic control of the chemical boundary conditions in situ, by which the crystal habit, and thus growth mode, can be actively engineered. In so doing, we establish the capability for layer-by-layer deposition in systems that otherwise default to island formation and grainy morphology. This technique is demonstrated via atomically smooth {111} calcium oxide films on (0001) gallium nitride. The operative surfactant-based mechanism is verified by temperature-dependent predictions from ab initio thermodynamic calculations. Calcium oxide films with smooth morphology exhibit a three order of magnitude enhancement of insulation resistance.}, journal={NATURE COMMUNICATIONS}, author={Paisley, Elizabeth A. and Losego, Mark. D. and Gaddy, Benjamin E. and Tweedie, James S. and Collazo, Ramon and Sitar, Zlatko and Irving, Douglas L. and Maria, Jon-Paul}, year={2011}, month={Sep} }
 @article{haridasan_lam_feng_fathelbab_maria_kingon_steer_2011, title={Tunable ferroelectric microwave bandpass filters optimised for system-level integration}, volume={5}, ISSN={["1751-8733"]}, DOI={10.1049/iet-map.2010.0461}, abstractNote={Tunable bandpass filters are critical components in emerging radio frequency front-ends. A system-aware design guideline and figure of merit (FOM) are developed for optimum system-level performance. The optimisation metric discussed here deviates from earlier guidelines as the filter bandwidth is allowed to vary in the tunable range, constrained only by the downstream system analogue to digital converter. The system-aware FOM uses worst-case filter design parameters and a tuning sensitivity term that captures the frequency tunability relative to material tunability. A 6.74-8.23-GHz tunable barium strontium titanate-based filter is presented as an example to illustrate the design methodology.}, number={10}, journal={IET MICROWAVES ANTENNAS & PROPAGATION}, author={Haridasan, V. and Lam, P. G. and Feng, Z. and Fathelbab, W. M. and Maria, J-P. and Kingon, A. I. and Steer, M. B.}, year={2011}, month={Jul}, pages={1234–1241} }
 @article{bradford_wang_zhao_maria_jia_zhu_2010, title={A novel approach to fabricate high volume fraction nanocomposites with long aligned carbon nanotubes}, volume={70}, ISSN={["1879-1050"]}, DOI={10.1016/j.compscitech.2010.07.020}, abstractNote={Conventional micro-fiber-reinforced composites provide insight into critical structural features needed for obtaining maximum composite strength and stiffness: the reinforcements should be long, well aligned in a unidirectional orientation, and should have a high reinforcement volume fraction. It has long been a challenge for researchers to process CNT composites with such structural features. Here we report a method to quickly produce macroscopic CNT composites with a high volume fraction of millimeter long, well aligned CNTs. Specifically, we use the novel method, shear pressing, to process tall, vertically aligned CNT arrays into dense aligned CNT preforms, which are subsequently processed into composites. Alignment was confirmed through SEM analysis while a CNT volume fraction in the composites was calculated to be 27%, based on thermogravimetric analysis data. Tensile testing of the preforms and composites showed promising mechanical properties with tensile strengths reaching 400 MPa.}, number={13}, journal={COMPOSITES SCIENCE AND TECHNOLOGY}, author={Bradford, Philip D. and Wang, Xin and Zhao, Haibo and Maria, Jon-Paul and Jia, Quanxi and Zhu, Y. T.}, year={2010}, month={Nov}, pages={1980–1985} }
 @article{losego_craft_paisley_mita_collazo_sitar_maria_2010, title={Critical examination of growth rate for magnesium oxide (MgO) thin films deposited by molecular beam epitaxy with a molecular oxygen flux}, volume={25}, ISSN={["0884-2914"]}, DOI={10.1557/jmr.2010.0096}, abstractNote={The authors report a study of molecular beam deposition of MgO films on amorphous SiO2 and (0001) GaN surfaces over a large range of temperatures (25–400 °C) and molecular oxygen growth pressures (10−7–10−4 Torr). This study provides insight into the growth behavior of an oxide with volatile metal constituents. Unlike other materials containing volatile constituents (e.g., GaAs, PbTiO3), all components of MgO become volatile at normal epitaxial growth temperatures (≥250 °C). Consequently, defining which species is the adsorption controller becomes ambiguous. Different growth regimes are delineated by the critical substrate temperature for Mg re-evaporation and the Mg:O flux ratio. These regimes have impact on phase purity, quartz crystal microbalance calibration, and film microstructure. The universal decay in deposition rate above growth 10−5 Torr O2 is also considered. By introducing a third flux of inert argon gas, rate reduction is attributed to increased molecular scattering and not oxidation of the metal source.}, number={4}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Losego, Mark D. and Craft, H. Spalding and Paisley, Elizabeth A. and Mita, Seiji and Collazo, Ramon and Sitar, Zlatko and Maria, Jon-Paul}, year={2010}, month={Apr}, pages={670–679} }
 @article{aygun_daniels_borland_maria_2010, title={In situ methods to explore microstructure evolution in chemically derived oxide thin films}, volume={25}, ISSN={["0884-2914"]}, DOI={10.1557/jmr.2010.0066}, abstractNote={In situ residual gas analyzer techniques were used to identify process-property relationships that regulate microstructure evolution in chemical solution-deposited BaTiO3films. In situ analysis of furnace exhaust gasses enabled quantitative exploration of thermolysis and crystallization reactions and an ability to identify processing parameters that influence the temperature ranges over which they occur. The atmospheric analysis was instrumental in identifying heat treatments that produced optimally consolidated precursor gels that crystallized into BaTiO3layers with optimized structure and properties. Slow ramp rates resulted in higher porosity, larger grain size, and a dramatic drop in the capacitor yield. Fast ramp rates produced similar trends; however, the mechanisms were distinct. The effects of oxygen partial pressure were also explored. BaTiO3grain size increased with increasing pO2, whereas there was no appreciable influence on density and capacitor yield. Optimal firing parameters, i.e., 20 °C/min ramp rate at a pO2of 10−13atm, were identified as those that produced an overlap in the temperature ranges of thermolysis and crystallization reactions and thus a precursor gel with a density and compliance that supports crystallization and densification while tolerating the associated volume contraction. This in situ approach to analyze downstream furnace gas is shown to be a generically applicable means to understand synthesis methods that are complicated by simultaneous mechanisms of precursor decomposition, extraction of volatile components, and crystallization.}, number={3}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Aygun, Seymen M. and Daniels, Patrick and Borland, William J. and Maria, Jon-Paul}, year={2010}, month={Mar}, pages={427–436} }
 @misc{brennecka_ihlefeld_maria_tuttle_clem_2010, title={Processing Technologies for High-Permittivity Thin Films in Capacitor Applications}, volume={93}, ISSN={["1551-2916"]}, DOI={10.1111/j.1551-2916.2010.04211.x}, abstractNote={Capacitor technologies are as varied as the applications that they enable, but one of the common themes in advanced capacitors for consumer electronics is a desire for increased capacitance in smaller areas/volumes. The heroic advances of discrete capacitor manufacturers have kept pace with the increasing demands of miniaturization, but a time is quickly approaching when it appears that powder‐based fabrication techniques simply will not be able to achieve desired layer thicknesses and capacitance densities. Here, we review the current state of the art and recent advances in the processing science and technology of high‐permittivity thin films with a focus on industrially scalable solution‐based fabrication processes of perovskite ferroelectric systems that appear to offer the greatest promise for the fabrication of future nanoscale capacitors.}, number={12}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Brennecka, Geoff L. and Ihlefeld, Jon F. and Maria, Jon-Paul and Tuttle, Bruce A. and Clem, Paul G.}, year={2010}, month={Dec}, pages={3935–3954} }
 @article{ihlefeld_daniels_aygun_borland_maria_2010, title={Property engineering in BaTiO3 films by stoichiometry control}, volume={25}, ISSN={["2044-5326"]}, DOI={10.1557/jmr.2010.0151}, abstractNote={BaTiO3 thin films were prepared on metallic foil substrates using chemical solution deposition. The impact of A to B site cation ratios on the phase assemblage and microstructural and dielectric properties was investigated by characterizing a sample set that includes stoichiometric BaTiO3 and 1, 2, 3, 4, and 5 mol% excess BaO. Each composition was subjected to a high-temperature anneal step with maximum dwell temperatures of 1000, 1100, and 1200 °C for 20 h. Excess barium concentrations greater than 3% lead to dramatic grain growth and average grain sizes exceeding 1 μm. Despite the large deviations from stoichiometry and the 20 h dwell time at temperature, x-ray diffraction, and high-resolution electron microscopy analysis were unable to detect secondary phases until films with 5% excess barium were annealed to 1200 °C. Thin films with 3% excess barium were prepared on copper substrates and annealed at 1060 °C, the practical limit for copper. This combination of BaO excess and annealing temperature produced an average lateral grain size of 0.8 μm and a room-temperature permittivity of 4000. This is in comparison to a permittivity of 1800 for stoichiometric material prepared using identical conditions. This work suggests metastable solubility of BaO in BaTiO3 that leads to enhanced grain growth and large permittivity values. This technique provides a new solid-state means of achieving grain growth in low thermal budget systems.}, number={6}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Ihlefeld, J. F. and Daniels, P. R. and Aygun, S. M. and Borland, W. J. and Maria, J-P.}, year={2010}, month={Jun}, pages={1064–1071} }
 @article{losego_maria_2010, title={Reproducibility and Ferroelectric Fatigue of Lead Zirconate Titanate Thin Films Deposited Directly on Copper Via a Composite Gel Architecture}, volume={93}, ISSN={["0002-7820"]}, DOI={10.1111/j.1551-2916.2010.04176.x}, abstractNote={ Integrating ferroelectric lead zirconate titanate (PZT) thin films directly on copper metal foils has high commercialization potential. PZT films on copper foils eliminate costly noble metal or conductive oxide electrodes and make available a flexible substrate technology that can be readily laminated into printed wiring boards. Unlike noble metals, copper substrates are potentially reactive, and therefore susceptible to processing fluctuations that offer negligible consequences to noble metal‐based systems. Herein, the reliability of the composite gel architecture route for synthesizing PZT thin films directly on copper foils is explored. Reproducibility in film properties and avoidance of solution aging effects are demonstrated. Fatigue cycling is used to evaluate electrical durability. Ferroelectric switching with polarization saturation is demonstrated after 1 billion cycles. Loss in spontaneous polarization is recovered with postfatigue annealing demonstrating the high material integrity necessary for commercial device performance, and distinct similarity to the behavior over time with noble metal electrode capacitors. }, number={12}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Losego, Mark D. and Maria, Jon-Paul}, year={2010}, month={Dec}, pages={3983–3985} }
 @misc{borland_burn_ihlefeld_maria_suh_2009, title={Articles comprising manganese doped barium titanate thin film compositions}, volume={7,572,518}, number={2009 Aug. 11}, author={Borland, W. and Burn, I. and Ihlefeld, J. F. and Maria, J. P. and Suh, S.}, year={2009} }
 @article{losego_efremenko_rhodes_cerruti_franzen_maria_2009, title={Conductive oxide thin films: Model systems for understanding and controlling surface plasmon resonance}, volume={106}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.3174440}, DOI={10.1063/1.3174440}, abstractNote={Degeneratively doped conductive oxides represent a unique host for exploring the inter-relationship between the properties of charge carriers and their collective plasmonic response. These materials often lack interband transitions that obfuscate interpretation of spectral response in elemental metals, and unlike metals, the electronic transport properties of conductive oxides are easily tunable. This work explores the process-structure-property relationships that regulate surface plasmon resonance (SPR) in sputter deposited indium tin oxide (ITO) thin films. Film deposition conditions are used to regulate film microstructure and tune the electronic mobility to between 7 and 40 cm2 V−1 s−1. Postdeposition annealing in low oxygen partial pressure atmospheres is used to engineer the ITO defect equilibrium and modulate carrier concentrations to between 1020 and 1021 cm−3. These electronic transport properties are modulated with near independence enabling straightforward interpretation of their influence on the SPR response observed in the infrared reflectivity spectrum. Higher electronic mobilities favor narrower surface plasmon absorption bands, while higher carrier concentrations favor higher absorption band frequencies. A simple free electron model, having only electronic carrier density and electronic mobility as variables, can be used to describe ITO’s dielectric response. Calculations that combine this dielectric function and the Fresnel equations provide simulated reflectivity spectra that match experimental data with remarkable accuracy. Because these spectra use no fitting parameters and are calculated with well-studied material properties, it opens the opportunity for future design of plasmonic response in advanced material systems including degeneratively doped semiconductors, silicides, and nitrides.}, number={2}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Losego, Mark D. and Efremenko, Alina Y. and Rhodes, Crissy L. and Cerruti, Marta G. and Franzen, Stefan and Maria, Jon-Paul}, year={2009}, month={Jul}, pages={024903} }
 @article{losego_fitting kourkoutis_mita_craft_muller_collazo_sitar_maria_2009, title={Epitaxial Ba0.5Sr0.5TiO3–GaN heterostructures with abrupt interfaces}, volume={311}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2008.11.085}, DOI={10.1016/j.jcrysgro.2008.11.085}, abstractNote={Abstract Epitaxial heterostructures incorporating the complex ferroelectric oxide Ba 0.5 Sr 0.5 TiO 3 (BST) and GaN were prepared using a combination of RF magnetron sputtering and metalorganic chemical vapor deposition for the respective layers. The heterostructures were grown on c -plane sapphire substrates and were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning transmission electron microscopy (STEM). This analysis showed that at substrate temperatures of 650 °C, BST films grow epitaxially on GaN with a {1 1 1} orientation and that the GaN–BST interface is smooth and abrupt, with disorder confined to grain boundaries and the interface plane. The film morphology is grainy indicating a 3-D growth mode. High-temperature post-deposition annealing studies suggest no interface reactions up to 900 °C. These results demonstrate that complex oxides like BST can be integrated with wide bandgap semiconductors like GaN and open exciting possibilities for new multifunctional devices.}, number={4}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Losego, M.D. and Fitting Kourkoutis, L. and Mita, S. and Craft, H.S. and Muller, D.A. and Collazo, R. and Sitar, Z. and Maria, J.-P.}, year={2009}, month={Feb}, pages={1106–1109} }
 @misc{borland_burn_ihlefeld_maria_suh_2009, title={Methods of making thin film capacitors comprising a manganese doped barium titantate dielectric}, volume={7,601,181}, number={2009 Oct. 13}, author={Borland, W. and Burn, I. and Ihlefeld, J. F. and Maria, J. P. and Suh, S.}, year={2009} }
 @article{franzen_rhodes_cerruti_gerber_losego_maria_aspnes_2009, title={Plasmonic phenomena in indium tin oxide and ITO-Au hybrid films}, volume={34}, ISSN={["1539-4794"]}, DOI={10.1364/OL.34.002867}, abstractNote={The observation of surface-plasmon resonances in indium tin oxide (ITO) thin films is complemented with the effects of hybrid ITO/Au conducting layers where charge densities can be tuned. Where carrier densities are similar (ITO and nanoparticle Au), the plasmonic behavior is that of a monolithic ITO thin film. Where the carrier density of one layer is much greater than that of the other (ITO and Au metal), boundary conditions lead to cancelation of the surface plasmon. In the latter case a capacitivelike plasmon resonance is observed for sufficiently thin films.}, number={18}, journal={OPTICS LETTERS}, author={Franzen, Stefan and Rhodes, Crissy and Cerruti, Marta and Gerber, Ralph W. and Losego, Mark and Maria, Jon-Paul and Aspnes, D. E.}, year={2009}, month={Sep}, pages={2867–2869} }
 @article{lam_feng_haridasan_kingon_steer_maria_2009, title={The Impact of Metallization Thickness and Geometry for X-Band Tunable Microwave Filters}, volume={56}, ISSN={["1525-8955"]}, DOI={10.1109/TUFFC.2009.1122}, abstractNote={The impact of dc resistance on the performance of X-band filters with ferroelectric varactors was investigated. Two series of combline bandpass filters with specific geometries to isolate sources of conductor losses were designed and synthesized. Combining the changes in filter geometry with microwave measurements and planar filter solver (Sonnet software) simulations quantitatively identified the dependency of insertion loss on overall metallization thickness and local regions of thin metallization. The optimized 8-GHz bandpass filters exhibited insertion losses of 6.8 dB. These filters required 2.5 ¿m of metal thickness (or 3 effective skin depths) to achieve this loss. The trend of loss with thickness indicates diminishing return with additional metal. The integration scheme requires thin regions of metal in the immediate vicinity of the varactors. It is shown through experiment and simulation that short distances (i.e., 15 ¿m) of thin metallization can be tolerated provided that they are located in regions where the resonant microwave current is low.}, number={5}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, author={Lam, Peter G. and Feng, Zhiping and Haridasan, Vrinda and Kingon, Angus I. and Steer, Michael B. and Maria, Jon-Paul}, year={2009}, month={May}, pages={906–911} }
 @article{paisley_losego_aygun_craft_maria_2008, title={Barrier layer mechanism engineering in calcium copper titanate thin film capacitors through microstructure control}, volume={104}, ISSN={["1089-7550"]}, DOI={10.1063/1.3033166}, abstractNote={A peak permittivity greater than 10 000 has been achieved for calcium copper titanate (CCT) thin films by engineering a thin film microstructure that maximizes space charge contributions to polarizability. This permittivity is an order of magnitude greater than previous polycrystalline thin film efforts. This unique microstructure control is accomplished using a chemical solution deposition process flow that produces highly dense parallel layers ∼100 nm in thickness. We observe a thickness dependent permittivity where the entire film thickness constitutes the conducting region of a barrier layer capacitor despite the presence of multiple grain boundaries within that thickness. The model predictions are in good agreement with experimental data and are consistent with existing literature reports. These trends in permittivity with dielectric thickness raise new questions regarding the nature of barrier layers in CCT—and specifically, these results suggest that grain boundaries may not always participate as high resistance interlayers.}, number={11}, journal={JOURNAL OF APPLIED PHYSICS}, author={Paisley, E. A. and Losego, M. D. and Aygun, S. M. and Craft, H. S. and Maria, J. -P.}, year={2008}, month={Dec} }
 @article{ihlefeld_losego_collazo_borland_maria_2008, title={Defect chemistry of nano-grained barium titanate films}, volume={43}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-007-2135-3}, number={1}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Ihlefeld, Jon F. and Losego, Mark D. and Collazo, Ramon and Borland, William J. and Maria, Jon-Paul}, year={2008}, month={Jan}, pages={38–42} }
 @article{rhodes_cerruti_efremenko_losego_aspnes_maria_franzen_2008, title={Dependence of plasmon polaritons on the thickness of indium tin oxide thin films}, volume={103}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.2908862}, DOI={10.1063/1.2908862}, abstractNote={The evolution of polariton features with increasing thickness in p-polarized (TM) reflectance spectra of indium tin oxide (ITO) thin films deposited on BK7 glass reveals the nature of plasmons in conducting thin films without interference from band-to-band transitions or the tendency of very thin films to form islands, both of which are complicating factors with the noble metals Au and Ag. Although the dependence on energy, film thickness, and angle of incidence is complex, these features are accurately described by the three-phase (substrate/overlayer/ambient) Fresnel model using only the Drude free-electron representation for the dielectric function of the ITO film. For film thicknesses less than 80nm the relevant excitation is a one-dimensional screened-bulk plasmon (SBP) that corresponds to charge transfer across the entire film. The associated SBP polariton (SBPP) occurs at the energy of the SBP and is relatively independent of the angle of incidence. For film thicknesses greater than 120nm, the relevant excitation is the surface plasmons (SP). The associated surface plasmon polariton (SPP) exhibits the usual strong dependence of energy on the angle of incidence. For larger thicknesses this structure gradually weakens, in agreement with theory. No other collective excitations are observed. The optimum thicknesses for the SPP in ITO is 160nm, whereas the SBPP is observed only when the film thickness is less than 70nm. The SBPP exhibits many of the features that make the SPP attractive for both science and technology, but has not been observed previously. Our results show that ITO films, in particular, and conducting-metal-oxide films in general provide new opportunities for investigating plasmons in conductors and obtaining new insights into plasmons, plasmon polaritons, and related optical phenomena.}, number={9}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Rhodes, C. and Cerruti, M. and Efremenko, A. and Losego, M. and Aspnes, D. E. and Maria, J.-P. and Franzen, S.}, year={2008}, month={May}, pages={093108} }
 @article{ihlefeld_borland_maria_2008, title={Dielectric and microstructural properties of barium titanate hafhate thin films}, volume={516}, DOI={10.1016/j.tsf.2007.08.096}, abstractNote={Barium titanate hafnate (BaTi1−xHfxO3, 0 ≤ x ≤ 0.25) thin films have been deposited by a chemical solution method on copper foil substrates. The films were crystallized at 900 °C and in a reducing atmosphere to prevent substrate oxidation. Perovskite phase formation was identified for each composition, accompanied by an increased pseudocubic lattice parameter. Temperature dependent dielectric measurements revealed a decreasing phase transition temperature and peak permittivity with increasing hafnium level. The decrease in permittivity resulted from grain size reduction with increasing hafnium content. Compositions containing 25 mol% barium hafnate display a deviation from Curie–Weiss behavior indicating the onset of relaxor behavior.}, number={10}, journal={Thin Solid Films}, author={Ihlefeld, J. F. and Borland, W. J. and Maria, J. P.}, year={2008}, pages={3162–3166} }
 @article{ihlefeld_borland_maria_2008, title={Enhanced dielectric tunability in barium titanate thin films with boron additions}, volume={58}, ISSN={["1359-6462"]}, DOI={10.1016/j.scriptamat.2007.11.008}, abstractNote={Boron incorporation in 650 nm thick polycrystalline BaTiO3 films results in grain growth and dramatic dielectric response improvements. For levels between 0% and 3%, average grain size is increased from 150 to 200 nm and the maximum permittivity values are nearly doubled, with tunabilities increased to greater than 90% while maintaining high field loss tangents below 0.03. These results demonstrate a pathway for microstructure engineering and property optimization in refractory electroceramic oxide thin films without increasing the thermal budget.}, number={7}, journal={SCRIPTA MATERIALIA}, author={Ihlefeld, Jon F. and Borland, William J. and Maria, Jon-Paul}, year={2008}, month={Apr}, pages={549–552} }
 @article{losego_mita_collazo_sitar_maria_2008, title={Epitaxial growth of the metastable phase ytterbium monoxide on gallium nitride surfaces}, volume={310}, ISSN={["0022-0248"]}, DOI={10.1016/j.jcrysgro.2007.10.002}, abstractNote={Molecular beam deposition systems allow for unparalleled control of film composition and structure. This article addresses the capacity for controlling metal and oxidant fluxes in the Yb/O2 system to access the metastable phase ytterbium monoxide (YbO). Experiments exploring the growth of polycrystalline YbOx films by molecular beam deposition demonstrate that a 2:1 molar ratio of Yb:O2 fluxes is necessary to achieve preferential growth of the divalent oxide. Applying similar deposition conditions to a (0 0 1) GaN surface leads to the growth of epitaxial (1 1 1) YbO films. Similar to other rocksalt oxides grown on GaN surfaces, YbO films display a 3D growth mechanism that leads to a grainy morphology with crystallites of 50 nm lateral dimensions. Rocking curves in ω and φ have full-width half-maximum values of 1.77° and 4.1°, respectively; further improvements in crystal quality appear to be limited by the thermal stability of the YbO phase.}, number={1}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Losego, Mark D. and Mita, Seiji and Collazo, Ramon and Sitar, Zlatko and Maria, Jon-Paul}, year={2008}, month={Jan}, pages={51–56} }
 @article{ihlefeld_vodnick_baker_borland_maria_2008, title={Extrinsic scaling effects on the dielectric response of ferroelectric thin films}, volume={103}, ISSN={["1089-7550"]}, DOI={10.1063/1.2903211}, abstractNote={Scaling effects in polycrystalline ferroelectric thin films were investigated by preparing barium titanate in a manner that maintained constant composition and film thickness while allowing systematically increased grain size and crystalline coherence. The average grain dimensions ranged from 60to110nm, and temperature dependence of permittivity analysis revealed diffuse phase transitions in all cases. Maximum permittivity values ranged from 380 to 2040 for the smallest to largest sizes, respectively. Dielectric hysteresis is evident at room temperature for all materials, indicating stability of the ferroelectric phase. Comparison of permittivity values at high electric fields indicates that the intrinsic dielectric response is identical and microstructural artifacts likely have a minimal influence on film properties across the sample series. Permittivity values, however, are substantially smaller than those reported for bulk material with similar grain dimensions. X-ray line broadening measurements were taken for the grain size series at the Cornell High Energy Synchrotron Source (CHESS), which revealed coherent scattering dimensions substantially smaller than the microscopy-determined grain size. Collectively these data sets suggest that permittivity values are influenced not only by grain size but also by the mosaic structure existing within each grain, and that thin film thermal budgets, which are several hundred degrees lower than used for bulk processing, are responsible for reduced crystalline coherence, and likely the origin of degraded electromechanical response in thin film ferroelectrics.}, number={7}, journal={JOURNAL OF APPLIED PHYSICS}, author={Ihlefeld, Jon F. and Vodnick, Aaron M. and Baker, Shefford P. and Borland, William J. and Maria, Jon-Paul}, year={2008}, month={Apr} }
 @article{laughlin_ihlefeld_daniels_maria_2008, title={Flexible and lithography-compatible copper foil substrates for ferroelectric thin films}, volume={516}, ISSN={["0040-6090"]}, DOI={10.1016/j.tsf.2007.08.093}, abstractNote={A process has been developed for preparing a low surface roughness copper foil by evaporation and subsequent peel-off of copper metal layers on glass slides. These 15 micron thick substrates exhibited roughness values between 1 and 2 nm root-mean-square (RMS) and 9 nm RMS over 25 μm2 and 100 μm2 analysis areas, respectively. The deposition and crystallization of barium strontium titanate layers were demonstrated on these smoother variant foils. The fully processed dielectric layers exhibited field tunability greater than 5:1, and could withstand fields in excess of 750 kV/cm. High field loss tangents below 0.007 were observed, making these materials excellent candidates for microwave devices. Finally, a process of lamination and contact lithography was used to demonstrate patterning of micron-scale features suitable for microwave circuit element designs.}, number={10}, journal={THIN SOLID FILMS}, author={Laughlin, B. and Ihlefeld, J. F. and Daniels, Patrick and Maria, J. -P.}, year={2008}, month={Mar}, pages={3294–3297} }
 @article{lebeau_jur_lichtenwalner_craft_maria_kingon_klenov_cagnon_stemmer_2008, title={High temperature stability of Hf-based gate dielectric stacks with rare-earth oxide layers for threshold voltage control}, volume={92}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.2901036}, DOI={10.1063/1.2901036}, abstractNote={The thermal stability of DyOx∕HfSiON and HoOx∕HfSiON gate dielectric stacks on silicon was studied by scanning transmission electron microscopy techniques and correlated with their electrical characteristics. Intermixing of the rare-earth elements with the HfSiON was observed, but there was no diffusion into the interfacial SiO2. Rapid thermal annealing (1000°C) produced little detectable change in the concentration profile of the rare-earth elements but caused thinning of the interfacial SiO2 layer along with a corresponding increase in the rare-earth oxide layer thickness. These reactions could be explained with oxygen deficiency in the rare-earth oxide layer and its greater thermodynamic stability relative to SiO2. Negative flat band voltage shifts were observed relative to a control sample with no DyOx or HoOx. Mechanisms by which the observed microstructure changes could give rise to negative flatband voltage shifts are discussed.}, number={11}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={LeBeau, James M. and Jur, Jesse S. and Lichtenwalner, Daniel J. and Craft, H. Spalding and Maria, Jon-Paul and Kingon, Angus I. and Klenov, Dmitri O. and Cagnon, Joël and Stemmer, Susanne}, year={2008}, month={Mar}, pages={112912} }
 @article{aygun_daniels_borland_maria_2008, title={Hot sputtering of barium strontium titanate on nickel foils}, volume={103}, ISSN={["0021-8979"]}, DOI={10.1063/1.2909920}, abstractNote={The relationships linking temperature and voltage dependent dielectric response, grain size, and thermal budget during synthesis are illustrated. In doing so, it was found that maximizing thermal budgets within experimental bounds leads to electrical properties comparable to the best literature reports irrespective of the processing technique or microstructure. The optimal film properties include a bulk transition temperature, a room temperature permittivity of 1800, a voltage tuning ratio of 10:1 at 450 kV/cm, and a loss tangent less than 1.5% at 450 kV/cm. The sample set illustrates the well-known relationship between permittivity and crystal dimension, and the onset of a transition temperature shifts at very fine grain sizes. A brick wall model incorporating a high permittivity grain and a low permittivity grain boundary is used to interpret the dielectric data. However, the data show that high permittivity and tunability values can be achieved at grain sizes or film thicknesses that many reports associate with dramatic reductions in the dielectric response. These differences are discussed in terms of crystal quality and maximum processing temperature. The results collectively suggest that scaling effects in ferroelectric thin films are in many cases the result of low thermal budgets and the consequently high degree of structural imperfection and are not from the existence of low permittivity phases at the dielectric-electrode interface.}, number={8}, journal={JOURNAL OF APPLIED PHYSICS}, author={Aygun, Seymen M. and Daniels, Patrick and Borland, William and Maria, Jon-Paul}, year={2008}, month={Apr} }
 @article{losego_ihlefeld_maria_2008, title={Importance of solution chemistry in preparing sol-gel PZT thin films directly on copper surfaces}, volume={20}, ISSN={["0897-4756"]}, DOI={10.1021/cm070999q}, abstractNote={The ferroelectric material lead zirconate titanate (PZT) has traditionally been considered incompatible with base metal technology because PbO volatility makes conventional thermodynamic equilibrium processing impractical. However, by strategically designing solution chemistry and processing conditions to avoid interfacial reaction, chemical-solution-deposited PZT films can be prepared on copper surfaces without oxidizing the base metal or cracking the oxide film. A limited set of thermal and atmospheric processing conditions to kinetically maintain an unoxidized copper substrate are available and not necessarily optimal for processing sol–gel films. Solutions processed within these confined conditions must form gels with sufficiently reduced organic content and properly consolidated gel networks such that phase-pure and crack-free ceramic films can be crystallized. The current work explores three solution chemistries that use different chelating ligands: alkanolamines, acetylactone, and acetic acid. It i...}, number={1}, journal={CHEMISTRY OF MATERIALS}, author={Losego, Mark D. and Ihlefeld, Jon F. and Maria, Jon-Paul}, year={2008}, month={Jan}, pages={303–307} }
 @article{goodrich_cai_losego_maria_kourkoutis_muller_ziemer_2008, title={Improved epitaxy of barium titanate by molecular beam epitaxy through a single crystalline magnesium oxide template for integration on hexagonal silicon carbide}, volume={26}, ISSN={["2166-2746"]}, DOI={10.1116/1.2889389}, abstractNote={Crystalline MgO(111) has the potential to be an effective template for the heteroepitaxial integration of BTO(111) and other functional oxides on 6H-SiC(0001). Deposition of MgO on 6H-SiC(0001) at 140°C resulted in a twinned structure with only (111) orientation. By heating the MgO(111) after deposition to 650°C at a background pressure of 1.0×10−9Torr or depositing the MgO at 650°C, the twinned structure can be minimized, resulting in a reflection high energy electron diffraction (RHEED) pattern characteristic of random epitaxial islands. The use of a 2nm MgO(111) template layer proved optimal for deposition of crystalline BTO(111) by molecular beam epitaxy on 6H-SiC(0001). The BTO was found to be twinned with a 60° in-plane rotation. The grain formation of the BTO resulted in a transmission dominated RHEED pattern. Deposition of BTO at a higher substrate temperature resulted in large grain formation, 50nm in size, but an increased surface roughness of 1.4±0.1nm over a 1μm2 area. In order to integrate BTO in a multiferroic device with multilayers of BTO(111) and hexagonal ferrites, it will be necessary to optimize the processing conditions to establish a smoother BTO surface for the subsequent heteroepitaxy of the magnetic film.}, number={3}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Goodrich, T. L. and Cai, Z. and Losego, M. D. and Maria, J. -P. and Kourkoutis, L. Fitting and Muller, D. A. and Ziemer, K. S.}, year={2008}, month={May}, pages={1110–1114} }
 @article{craft_collazo_losego_mita_sitar_maria_2008, title={Spectroscopic analysis of the epitaxial CaO (111)-GaN (0002) interface}, volume={92}, ISSN={["0003-6951"]}, DOI={10.1063/1.2887878}, abstractNote={We report an x-ray photoelectron spectroscopy (XPS) study of the CaO∕GaN interface. Epitaxial films of CaO (111) were grown on GaN (0002) and analyzed in situ using XPS. We observe Stranski–Krastanov growth, in which CaO coalesces rapidly, then converts to a three-dimensional mode. Data suggest coalescence within the first nanometer of film growth, indicating growth behavior different from published reports of the analogous MgO–GaN system. We find 1.0±0.2eV for the valence band offset and a 2.5±0.2eV conduction band offset. The results are discussed in terms of their utility in oxide-nitride electronic devices.}, number={8}, journal={APPLIED PHYSICS LETTERS}, author={Craft, H. S. and Collazo, R. and Losego, M. D. and Mita, S. and Sitar, Z. and Maria, J. -P.}, year={2008}, month={Feb} }
 @article{craft_collazo_losego_sitar_maria_2008, title={Surface water reactivity of polycrystalline MgO and CaO films investigated using x-ray photoelectron spectroscopy}, volume={26}, ISSN={["0734-2101"]}, DOI={10.1116/1.3000058}, abstractNote={The authors report a study comparing the surface reactivities of the alkaline earth oxides MgO and CaO with respect to water vapor under ultrahigh and high vacuum conditions. Using x-ray photoelectron spectroscopy and a series of in vacuo exposures spanning ∼10−10Torr vacuum, to 10−6Torr flowing oxygen, the extent of surface hydroxylation was investigated by monitoring the O 1s photoelectron line. After the most aggressive exposures, the MgO surface reacted to form a maximum hydroxyl coverage of ∼1.3 ML (monolayer), while the CaO surface reached a maximum coverage of ∼3.0 ML. Both surface hydroxides could be removed by in vacuo thermal anneals; exposure to 250 and 500°C were required for MgO and CaO, respectively. These results are framed in terms of the suitability of these oxides in complex oxide-compound semiconductor heteroepitaxial multifunctional devices and with respect to understanding the development of surface morphology in epitaxial 111-oriented CaO and MgO thin films.}, number={6}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Craft, H. S. and Collazo, R. and Losego, M. D. and Sitar, Z. and Maria, J. -P.}, year={2008}, month={Nov}, pages={1507–1510} }
 @article{ihlefeld_borland_maria_2008, title={Synthesis and properties of barium titanate stannate thin films by chemical solution deposition}, volume={43}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-008-2618-x}, number={12}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Ihlefeld, Jon F. and Borland, William J. and Maria, Jon-Paul}, year={2008}, month={Jun}, pages={4264–4270} }
 @article{craft_collazo_losego_mita_sitar_maria_2007, title={Band offsets and growth mode of molecular beam epitaxy grown MgO (111) on GaN (0002) by x-ray photoelectron spectroscopy}, volume={102}, ISSN={["1089-7550"]}, DOI={10.1063/1.2785022}, abstractNote={MgO is a proposed dielectric for use as a tunneling barrier in devices integrating GaN and ferroelectric oxides. In this study, we present data regarding the growth mode and band offsets of MgO grown epitaxially on GaN (0002) surfaces using molecular beam epitaxy. Using in situ x-ray photoelectron spectroscopy (XPS) and molecular beam epitaxy, we determine, from sequential growth experiments, that the growth of MgO proceeds via the Volmer-Weber (three-dimensional) mode, and full coalescence of the film does not occur until approximately 12nm of MgO has been deposited. The observation of a three-dimensional growth mode is in agreement with previously published data. For the valence band offset, we find a value of 1.2±0.2eV, which corresponds to a 3.2eV conduction band offset. XPS measurements suggest a chemically abrupt interface and no effect on band lineup due to the slow coalescence behavior.}, number={7}, journal={JOURNAL OF APPLIED PHYSICS}, author={Craft, H. S. and Collazo, R. and Losego, M. D. and Mita, S. and Sitar, Z. and Maria, J.-P.}, year={2007}, month={Oct} }
 @article{ihlefeld_borland_maria_2007, title={Enhanced Dielectric and Crystalline Properties in Ferroelectric Barium Titanate Thin Films}, volume={17}, ISSN={1616-301X}, url={http://dx.doi.org/10.1002/adfm.200601159}, DOI={10.1002/adfm.200601159}, abstractNote={Abstract}, number={7}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Ihlefeld, J. F. and Borland, W. J. and Maria, J.-P.}, year={2007}, month={Mar}, pages={1199–1203} }
 @article{losego_mita_collazo_sitar_maria_2007, title={Epitaxial calcium oxide films deposited on gallium nitride surfaces}, volume={25}, ISSN={["1071-1023"]}, DOI={10.1116/1.2710243}, abstractNote={Solid solutions of rocksalt oxides are proposed for lattice-matched dielectrics in gallium nitride (GaN) electronics. This article explores the epitaxial growth of the rocksalt oxide calcium oxide (CaO) by molecular beam epitaxy on gallium nitride surfaces. As a possible end member to a rocksalt oxide solid solution, it is important to understand the processing space that allows for epitaxial CaO growth. Exposing the GaN surface to the oxidant flux prior to the metal flux is shown to be critical in eliminating polycrystalline growth. The effect of deposition temperature, metal flux, and oxidant flux on the film’s epitaxial crystalline quality is also examined. Optimal epitaxial quality is found for growth temperatures of ⩾600°C and near oxygen pressures of 10−6Torr. Thermal stability of the CaO∕GaN interface is experimentally evaluated. No reaction phases are observed by x-ray diffraction up to 850°C in air and >1100°C in a reducing atmosphere. However, CaO films are found to be extremely reactive with H2O, forming Ca(OH)2 within a few hours when exposed to ambient atmosphere at room temperature.}, number={3}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Losego, Mark D. and Mita, Seiji and Collazo, Ramon and Sitar, Zlatko and Maria, Jon-Paul}, year={2007}, pages={1029–1032} }
 @article{cerruti_rhodes_losego_efremenko_maria_fischer_franzen_genzer_2007, title={Influence of indium-tin oxide surface structure on the ordering and coverage of carboxylic acid and thiol monolayers}, volume={40}, ISSN={["1361-6463"]}, DOI={10.1088/0022-3727/40/14/016}, abstractNote={This paper analyses the variability of self-assembled monolayers (SAMs) formation on ITO depending on the substrate surface features. In particular, we report on the formation of carboxylic acid- and thiol-based SAMs on two lots of commercially prepared indium–tin oxide (ITO) thin films. Contact angle measurements, electrochemical experiments, and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy showed that the quality of monolayers formed differed substantially between the two ITO batches. Only one of the two ITO substrates was capable of forming well-organized thiol- and carboxylic acid-based SAMs. In order to rationalize these observations, atomic force microscopy and x-ray diffraction analyses were carried out, and SAMs were prepared on ITO substrates fabricated by sputtering in our laboratories. An attempt was made to influence the film microstructure and surface morphology by varying substrate temperatures during ITO deposition. Good-quality thiol and carboxylic acid SAMs were obtained on one of the ITO substrates prepared in-house. While our characterization could not single out conclusively one specific parameter in ITO surface structure that could be responsible for good SAMs formation, we could point out homogeneous surface morphology as a relevant factor for the quality of the SAMs. Evidence was also found for ITO crystallographic orientation to be a parameter influencing SAMs organization.}, number={14}, journal={JOURNAL OF PHYSICS D-APPLIED PHYSICS}, author={Cerruti, Marta and Rhodes, Crissy and Losego, Mark and Efremenko, Alina and Maria, Jon-Paul and Fischer, Daniel and Franzen, Stefan and Genzer, Jan}, year={2007}, month={Jul}, pages={4212–4221} }
 @article{kim_kingon_maria_croswell_2007, title={Lead zirconate titanate thin film capacitors on electroless nickel coated copper foils for embedded passive applications}, volume={515}, ISSN={["0040-6090"]}, DOI={10.1016/j.tsf.2007.02.085}, abstractNote={Lead zirconate titanate (PZT, 52/48) thin film capacitors were prepared on electroless Ni coated Cu foil by chemical solution deposition for printed wiring board embedded capacitor applications. Phase development, dielectric properties, and leakage characteristics of capacitors were investigated, in particular as a function of the process temperature. Dielectric properties of the capacitors were dependent on the crystallization temperature, and capacitance densities of more than 350 nF/cm2 and loss tangent of less than 0.03 were measured for capacitors crystallized below 600 °C. Lowest leakage current densities (around 2 × 10− 7 A/cm2 at 10 V direct current (DC)) and highest breakdown fields could be obtained for capacitors crystallized at 650 °C. Capacitors with different thickness and a two-layer capacitor model were used in analyzing the interface layer between PZT and the underlying electroless Ni. From the capacitance and leakage measurements, it is suggested that the interface reaction layer has low permittivity (K around 30) and high defect concentration, which has an important effect on the electrical properties of capacitors. This interface is from the reaction of the electroless nickel layer with the adjacent PZT, and may specifically be moderated by the nickel phosphide (Ni–P) phase, transformed from amorphous Ni during the annealing step. The results have significant implications for embedded capacitors in printed wiring boards. They demonstrate that the process can be tuned to produce either voltage independent capacitors with low leakage and high breakdown fields (above 30 V DC), or the more usual hysteretic, switching, ferroelectric capacitors with higher capacitance densities.}, number={18}, journal={THIN SOLID FILMS}, author={Kim, Taeyun and Kingon, Angus I. and Maria, Jon-Paul and Croswell, Robert T.}, year={2007}, month={Jun}, pages={7331–7336} }
 @article{daniels_ihlefeld_borland_maria_2007, title={Smart electrodes for ultralarge-area thin film capacitors}, volume={22}, ISSN={["0884-2914"]}, DOI={10.1557/JMR.2007.0272}, abstractNote={A process suitable for preparing metal-insulator-metal thin film capacitors with submicron insulating layers and top electrodes with cm-scale dimensions is presented. Most importantly, this process does not require sophisticated deposition equipment or a clean room environment. The key to large area yield is co-firing the insulator film with a non-dewetting electrode during the dielectric crystallization/densification anneal. We propose a mechanism of electrode dewetting during the high temperature anneal where the metal laterally retreats from geometric asperities that compromise the integrity of the insulating layer. This behavior is driven by surface energy minimization, which promotes metal migration away from the regions of high curvature. This methodology is not material specific, and only requires a top electrode with a large contact angle to the dielectric in question. Using this technique, functional thin film capacitors with 2.5 cm lateral dimensions and 1 μm dielectric thicknesses can be routinely prepared.}, number={7}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Daniels, Patrick and Ihlefeld, Jon and Borland, William and Maria, Jon-Paul}, year={2007}, month={Jul}, pages={1763–1766} }
 @article{goodrich_cai_losego_maria_ziemer_2007, title={Thin, crystalline MgO on hexagonal 6H-SIC(0001) by molecular beam epitaxy for functional oxide integration}, volume={25}, ISSN={["2166-2746"]}, DOI={10.1116/1.2734979}, abstractNote={MgO thin films are proposed as a template for the effective integration of three and four element oxides on wide band gap SiC for next generation multifunctional devices. Oriented, crystalline MgO(111) of 20–380Å is grown on 6H-SiC(0001) by molecular beam epitaxy at a substrate temperature of 140°C using a magnesium effusion cell and a remote oxygen plasma source with ion deflection plates located at the end of the plasma discharge tube and approximately 7in. from the sample surface. Films are conformal to the steps of the cleaned SiC surface with a rms roughness of 0.45±0.05nm. Magnesium adsorption controls the growth rate in an excess oxygen environment with Mg:O flux ratios of 1:99–1:20, where the oxygen flux is the equivalent molecular oxygen. The oxygen plasma, which was determined to be free of ions when the ion deflection plates are energized, does impact nucleation and initial stages of the MgO film formation, and there may be evidence of etching mechanisms involved in the thicker film growth. Chemical and structural thermal stability of 20Å MgO(111)‖6H-SiC(0001) was demonstrated up to 740°C in vacuum for 90min through reflection high-energy electron diffraction and x-ray photoelectron spectroscopy analyses. X-ray diffraction was used to further test the thermal stability of 380Å films in vacuum and in an oxygen environment up to 790°C. As a proof of concept for MgO(111) as an interface for aligned functional oxide growth, barium titanate (111) was deposited on 100Å MgO(111)‖6H-SiC(0001) by rf magnetron sputtering.}, number={3}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Goodrich, T. L. and Cai, Z. and Losego, M. D. and Maria, J.-P. and Ziemer, K. S.}, year={2007}, pages={1033–1038} }
 @article{nath_fathelbab_lam_ghosh_aygun_gard_maria_kingon_steer_2006, title={Discrete Barium Strontium Titanate (BST) thin-film interdigital varactors on alumina: Design, fabrication, characterization, and applications}, ISBN={["978-0-7803-9541-1"]}, ISSN={["2576-7216"]}, DOI={10.1109/mwsym.2006.249652}, abstractNote={Discrete barium strontium titanate (BST) thin-film capacitors in industry standard 0603 footprint are introduced and characterized. BST capacitors have a voltage-dependent permittivity, enabling BST thin-film capacitors to be used as tuning elements in frequency agile devices. The capacitance changed by 1.5:1 at 35 V (116 kV/cm) bias. The temperature dependence of the capacitance was measured to be less than plusmn 20 % from -100 degC to +100 degC. A 2nd-order tunable combline bandpass filter on FR4 substrate has been implemented using the discrete BST varactors. The filter showed a center frequency tuning of 22% from 2.14 GHz to 2.61 GHz upon application of 130 V (433 kV/cm) bias. The zero-bias insertion loss was 4.9 dB which decreased to 2.9 dB at the high bias state. The return loss was better than 11 dB over the tuning range. Nonlinear characterization of the filter using two-tone test and a digitally-modulated CDMA 2000 signal showed an IP3 of +32 dBm and an ACPR of better than -50 dBc up to 26 dBm of input power, respectively}, journal={2006 IEEE MTT-S INTERNATIONAL MICROWAVE SYMPOSIUM DIGEST, VOLS 1-5}, author={Nath, Jayesh and Fathelbab, Wael M. and Lam, Peter G. and Ghosh, Dipankar and Aygun, Seymen and Gard, Kevin G. and Maria, J. -P. and Kingon, Angus I. and Steer, Michael B.}, year={2006}, pages={552–555} }
 @article{kim_kingon_maria_croswell_2006, title={Electrical properties of lead zirconate titanate thin films with a ZrO2 buffer layer on an electroless Ni-coated Cu foil}, volume={89}, ISSN={["1551-2916"]}, DOI={10.1111/j.1551-2916.2006.01240.x}, abstractNote={ The effect of zirconia (ZrO2) buffer layers on the phase development and electrical properties of lead zirconate titanate (PZT, 52/48) capacitors on an electroless Ni (P)‐coated Cu foil was investigated. It was demonstrated that the buffer layer can be used to engineer the final properties. The incorporation of the ZrO2 buffer layers retained acceptable capacitance densities (>350 nF/cm2 for 50 nm thick ZrO2), while significantly reducing leakage currents and improving reliability (<10−7 A/cm2 after 1 h at 25 VDC for 100 nm thick ZrO2), compared with PZT thin films directly on electroless Ni (P). The results are particularly important for embedded capacitor applications. }, number={11}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Kim, Taeyun and Kingon, Angus I. and Maria, Jon-Paul and Croswell, Robert T.}, year={2006}, month={Nov}, pages={3426–3430} }
 @article{craft_ihlefeld_losego_collazo_sitar_maria_2006, title={MgO epitaxy on GaN (0002) surfaces by molecular beam epitaxy}, volume={88}, ISSN={["1077-3118"]}, DOI={10.1063/1.2201041}, abstractNote={We report on the epitaxial deposition of magnesium oxide films with [111] crystallographic orientation on (0002) GaN by molecular beam epitaxy. Specifically, we use an adsorption controlled growth mechanism to initiate the growth process. Electron diffraction shows a spotty intense pattern without intensity fluctuations during growth and evidence of in-plane twinning. X-ray diffraction reveals the films to be epitaxial with full width at half maximum values of 0.3°, 0.5°, and 1° in 2θ, ϕ, and χ circles, respectively. Wet etching of the GaN surface with a HCl:HF mixture prior to growth is critical for achieving high crystalline quality. Epitaxial growth is observed between room temperature and 650°C, with negligible changes in crystalline quality with increased temperature. Atomic force microscopy analysis shows grainy surfaces with feature sizes near 10nm and rms roughness values of 1.4Å over 1μm2 areas. X-ray diffraction analysis suggests MgO film stability up to 850°C in ex situ air annealing.}, number={21}, journal={APPLIED PHYSICS LETTERS}, author={Craft, H. S. and Ihlefeld, J. F. and Losego, M. D. and Collazo, R. and Sitar, Z. and Maria, J. -P.}, year={2006}, month={May} }
 @article{craft_collazo_sitar_maria_2006, title={Molecular beam epitaxy of Sm2O3, Dy2O3, and Ho2O3 on Si (111)}, volume={24}, ISSN={["2166-2746"]}, DOI={10.1116/1.2216721}, abstractNote={We report on the epitaxial deposition of Sm2O3, Dy2O3, and Ho2O3 films on Si (111) substrates as progress towards developing a predictive model for gate oxide selection. To date, films have been characterized by reflection high-energy electron diffraction, x-ray diffraction (XRD), and x-ray photoemission spectroscopy (XPS). In the case of Sm2O3, difficulty was encountered in achieving the growth of phase pure films; growth of the desired bixbyite oxide phase was accompanied by significant amounts of monoclinic oxide as detected by XRD. Dy2O3 and Ho2O3 films can be produced free of unwanted phases when deposited using a background pressure of 1×10−6torr O2∕O3 and a substrate temperature between 425 and 550°C. Dy2O3 films with an x-ray peak width of 0.6° in ω were obtained. XPS studies of the Dy2O3∕Si interface are in progress, and verify the phase purity of the films.}, number={4}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Craft, H. S. and Collazo, R. and Sitar, Z. and Maria, J. P.}, year={2006}, pages={2105–2110} }
 @article{victor_nath_ghosh_boyette_maria_steer_kingon_stauf_2006, title={Noise characteristics of an oscillator with a barium strontium titanate (BST) varactor}, volume={153}, ISSN={["1350-2417"]}, DOI={10.1049/ip-map:20050068}, abstractNote={The phase noise of an oscillator with a thin-film barium strontium titanate (BST) capacitive tuning element, or varactor, is characterised and benchmarked against the same oscillator with a silicon semiconductor junction varactor. Phase noise tracks closely with varactor Q within a specific voltage range as expected. Compared to the semiconductor varactor-based oscillator, the BST-based oscillator demonstrates reduced phase noise degradation near zero volts, but greater phase noise degradation when operated near breakdown.}, number={1}, journal={IEE PROCEEDINGS-MICROWAVES ANTENNAS AND PROPAGATION}, author={Victor, A and Nath, J and Ghosh, D and Boyette, B and Maria, JP and Steer, MB and Kingon, AI and Stauf, GT}, year={2006}, month={Feb}, pages={96–102} }
 @misc{maria_kingon_2006, title={Structures including perovskite dielectric layers and variable oxygen concentration gradient layers}, volume={7,074,507}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Maria, J.-P. and Kingon, A. I.}, year={2006} }
 @article{rhodes_franzen_maria_losego_leonard_laughlin_duscher_weibel_2006, title={Surface plasmon resonance in conducting metal oxides}, volume={100}, ISSN={["1089-7550"]}, DOI={10.1063/1.2222070}, abstractNote={We report the initial observation of surface plasmon resonance (SPR) in a conducting metal oxide thin film. The SPR phenomenon has been observed by attenuated total reflection of near-infrared radiation and is in agreement with electron energy loss spectroscopy measurements. To date, only metals are known to exhibit surface plasmon resonance and only noble metals have practical application. According to theory SPR should be observable in any conductor. This theoretical prediction is verified in the present study. The compositions of many conducting metal oxides are systematically variable, suggesting a significant advance in thin film characterization and innovative possibilities for versatile and sensitive chemical sensing applications.}, number={5}, journal={JOURNAL OF APPLIED PHYSICS}, author={Rhodes, Crissy and Franzen, Stefan and Maria, Jon-Paul and Losego, Mark and Leonard, Donovan N. and Laughlin, Brian and Duscher, Gerd and Weibel, Stephen}, year={2006}, month={Sep} }
 @article{losego_maria_2006, title={Synthesis of polycrystalline ytterbium monoxide thin films by molecular beam deposition}, volume={24}, ISSN={["2166-2746"]}, DOI={10.1116/1.2214703}, abstractNote={The synthesis of ytterbium monoxide (YbO) by molecular beam deposition (MBD) is investigated for developing a lattice-matched oxide to gallium nitride. Because Yb2O3 is the thermodynamically stable oxide at atmospheric pressure, YbO has previously only been prepared by high-pressure bulk synthesis reactions. This article demonstrates that through low growth temperature and the kinetic control of molecular fluxes allowed by MBD, the polycrystalline monoxide phase can be stabilized in thin film form on silicon substrates. Once deposited, the YbO rocksalt structure is found to be stable at room temperature and atmospheric pressure. Elemental analysis indicates that films are primarily composed of Yb and O. Elemental concentrations of H, C, and N, which are known to form phases with Yb of similar structure and lattice parameter to YbO, are shown to be below the 1at.% level.}, number={4}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Losego, Mark D. and Maria, Jon-Paul}, year={2006}, pages={2111–2114} }
 @article{edge_schlom_rivillon_chabal_agustin_stemmer_lee_kim_craft_maria_et al._2006, title={Thermal stability of amorphous LaScO3 films on silicon}, volume={89}, ISSN={["1077-3118"]}, DOI={10.1063/1.2222302}, abstractNote={The thermal stability of amorphous LaScO3 thin films deposited by molecular-beam deposition directly on (001) Si was investigated by high-resolution transmission electron microscopy (HRTEM), transmission infrared absorption spectroscopy (IRAS), and x-ray diffraction (XRD). IRAS indicated that the as-deposited films contained <0.1Å of SiO2 at the interface between LaScO3 and silicon. XRD studies showed that the films remained amorphous after annealing in N2 at 700°C, although HRTEM showed structural order on an ∼1nm length scale even in the as-deposited films. By 800°C, the LaScO3 had started to crystallize and formed a ∼5nm thick Sc-deficient interlayer between it and silicon.}, number={6}, journal={APPLIED PHYSICS LETTERS}, author={Edge, L. F. and Schlom, D. G. and Rivillon, S. and Chabal, Y. J. and Agustin, M. P. and Stemmer, S. and Lee, T. and Kim, M. J. and Craft, H. S. and Maria, J. -P. and et al.}, year={2006}, month={Aug} }
 @misc{borland_ihlefeld_kingon_maria_2006, title={Thin film dielectrics for capacitors and methods of making thereof}, volume={7,029,971}, number={2006 Apr. 18}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Borland, W. J. and Ihlefeld, J. F. and Kingon, A. I. and Maria, J. P.}, year={2006} }
 @article{ghosh_laughlin_nath_kingon_steer_maria_2006, title={Tunable high-quality-factor interdigitated (Ba, Sr)TiO3 capacitors fabricated on low-cost substrates with copper metallization}, volume={496}, ISSN={["0040-6090"]}, DOI={10.1016/j.tsf.2005.09.025}, abstractNote={Interdigitated capacitors containing the field-tunable ferroelectric Ba0.75Sr0.25TiO3, polycrystalline alumina substrates, and copper metallization have been fabricated. Dielectric layers were prepared by magnetron sputtering, while the Cu metallization was evaporated. The dielectric tunability of the Ba0.75Sr0.25TiO3 was 40% at an applied electric field of 12 V/μm. This corresponds to a 3-μm electrode gap width and a 35 V dc bias. Low-frequency (1 MHz) loss tangent measurements indicate a dielectric Q (quality factor) of ∼100 while microwave measurements reveal a zero bias device Q of ∼30 at 26 GHz. These values are comparable or superior to numerous reports of barium strontium titanate interdigitated capacitors prepared using single crystalline substrates and noble metallization. As such, this technology is significantly less expensive and more amenable to large-volume manufacturing.}, number={2}, journal={THIN SOLID FILMS}, author={Ghosh, D and Laughlin, B and Nath, J and Kingon, AI and Steer, MB and Maria, JP}, year={2006}, month={Feb}, pages={669–673} }
 @inproceedings{victor_nath_ghosh_aygun_nagy_maria_kingon_steer_2006, title={Voltage controlled GaN on Si HFET power oscillator using thin?film ferroelectric varactor tuning}, DOI={10.1109/eumc.2006.281206}, abstractNote={A 1.6 GHz power oscillator with a GaN-on-Si heterostructure field effect transistor (HFET) is reported. The voltage-controlled oscillator used a thin-film barium strontium titanate (BST) interdigital varactor as the tuning element. The surface-mount varactor was fabricated using sputtered BST film and copper metallization on alumina. An output power of 1.6 W (32 dBm) is obtained with a DC conversion efficiency of 25.5%. Flat tuning sensitivity of 500 kHz/V, 49 MHz linear frequency tuning, and power flatness of better than 0.5 dB are obtained with 0-100 V tuning voltage. The maximum oscillator phase noise is -81.4 dBc/Hz at 100 kHz offset}, booktitle={Proceedings of the 36th European Microwave Conference, (EuMW2006), Manchester, UK}, publisher={London: Horizon House}, author={Victor, A. and Nath, J. and Ghosh, D. and Aygun, S. and Nagy, W. and Maria, J.-P. and Kingon, A. I. and Steer, M. B.}, year={2006}, pages={87–90} }
 @article{nath_ghosh_fathelbab_maria_kingon_franzon_steer_2005, title={A tunable combline bandpass filter using Barium Strontium Titanate interdigital varactors on an alumina substrate}, ISBN={["0-7803-8845-3"]}, ISSN={["2576-7216"]}, DOI={10.1109/mwsym.2005.1516670}, abstractNote={Barium strontium titanate (BST) has a field-dependent permittivity that enables it to be used as a dielectric in a voltage-tunable capacitor or varactor. A tunable combline bandpass filter was designed and characterized using BST varactors fabricated on a polycrystalline alumina substrate with copper metallization and is 14 mm /spl times/ 14 mm in size. The center frequency of the filter varies from 1.6 to 2.0 GHz with the application of 200 V tuning voltage. A 25% tuning range was achieved using tuning field strength of 300 kV/cm. The zero bias insertion loss was 6.6 dB and this decreased to 4.3 dB at the high bias state. The return loss was better than 10 dB.}, journal={2005 IEEE MTT-S INTERNATIONAL MICROWAVE SYMPOSIUM, VOLS 1-4}, publisher={Piscataway, NJ: IEEE}, author={Nath, J and Ghosh, D and Fathelbab, W and Maria, JP and Kingon, AI and Franzon, PD and Steer, MB}, year={2005}, pages={595–598} }
 @article{nath_ghosh_maria_kingon_fathelbab_franzon_steer_2005, title={An electronically tunable microstrip bandpass filter using thin-film barium-strontium-titanate (BST) varactors}, volume={53}, ISSN={["1557-9670"]}, DOI={10.1109/TMTT.2005.854196}, abstractNote={A tunable third-order combline bandpass filter using thin-film barium-strontium-titanate varactors and fabricated on a sapphire substrate is reported. Application of 0-200-V bias varied the center frequency of the filter from 2.44 to 2.88 GHz (16% tuning) while achieving a 1-dB bandwidth of 400 MHz. The insertion loss varied from 5.1 dB at zero bias to 3.3 dB at full bias, while the return loss exceeded 13 dB over the range. The third-order intercept of the filter was found to be 41 dBm.}, number={9}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Nath, J and Ghosh, D and Maria, JP and Kingon, AI and Fathelbab, W and Franzon, PD and Steer, MB}, year={2005}, month={Sep}, pages={2707–2712} }
 @article{maria_shepard_trolier-mckinstry_watkins_payzant_2005, title={Characterization of the piezoelectric properties of Pb0.98Ba0.02(Mg1/3Nb2/3)O-3-PbTiO3 epitaxial thin films}, volume={2}, ISSN={["1744-7402"]}, DOI={10.1111/j.1744-7402.2005.02004.x}, abstractNote={Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) (70/30) thin films were deposited by pulsed laser deposition using two growth strategies: adsorption controlled deposition from lead‐rich targets (∼25–30 mass%) and lower‐temperature deposition (Td≤600°C) from targets containing a small amount of excess lead oxide (≤3 mass %). The substrates used were (001) SrRuO3/LaAlO3. Typical remanent polarization values ranged between 12 and 14 μC/cm2 for these films. The longitudinal piezoelectric coefficient (d33,f) was measured using in situ four‐circle X‐ray diffraction, and the transverse coefficient (d31,f or e31,f) was measured using the wafer flexure method. d33,f and e31,f coefficients of ∼300–350 pm/V and ∼−11 C/m2 were calculated, respectively. In general, the piezoelectric coefficients and aging rates were strongly asymmetric, suggesting the presence of a polarization bias. The large, extremely stable piezoelectric response that results from poling parallel to the preferred polarization direction is attractive for miniaturized sensors and actuators.}, number={1}, journal={INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY}, author={Maria, JP and Shepard, JF and Trolier-McKinstry, S and Watkins, TR and Payzant, AE}, year={2005}, pages={51–58} }
 @article{ihlefeld_laughlin_hunt-lowery_borland_kingon_maria_2005, title={Copper compatible barium titanate thin films for embedded passives}, volume={14}, ISSN={["1573-8663"]}, DOI={10.1007/s10832-005-0866-6}, number={2}, journal={JOURNAL OF ELECTROCERAMICS}, author={Ihlefeld, J and Laughlin, B and Hunt-Lowery, A and Borland, W and Kingon, A and Maria, JP}, year={2005}, month={Mar}, pages={95–102} }
 @article{ihlefeld_maria_borland_2005, title={Dielectric and microstructural properties of barium titanate zirconate thin films on copper substrates}, volume={20}, ISSN={["2044-5326"]}, DOI={10.1557/JMR.2005.0342}, abstractNote={Barium titanate zirconate, Ba(Ti1−xZrx)O3 (0 ≤ x ≤ 0.25), thin films were deposited via the chemical solution deposition (CSD) method directly on copper foils. The films were processed in a reductive atmosphere containing nitrogen, water vapor, and hydrogen gas at 900 °C to preserve the metallic copper substrate during crystallization. Increasing the fraction of BaZrO3 revealed several effects, including an increase in unit cell dimensions, a decrease in both the temperature and value of the maximum permittivity, as well as a decrease in the average grain size of the films. The decrease in the relative permittivity was attributed to a grain size effect as opposed to zirconium substitution. In film compositions containing 25 mol% BaZrO3, the permittivity below Tmax became dispersive, and the ferroelectric transitions became increasingly diffuse. These characteristics suggest relaxor-like behavior. The dielectric tunability of Ba(Ti1−xZrx)O3 was studied at room temperature and at Tmax for each composition. There was little variation in the tunability with measurement temperature; however compositions that were ferroelectric at room temperature saw a decrease in hysteresis at Tmax, and all compositions showed an increase in permittivity.}, number={10}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Ihlefeld, JF and Maria, JP and Borland, W}, year={2005}, month={Oct}, pages={2838–2844} }
 @article{aygun_tan_maria_cann_2005, title={Effects of processing conditions on the dielectric properties of CaCu3Ti4O12}, volume={15}, ISSN={["1573-8663"]}, DOI={10.1007/s10832-005-3191-1}, number={3}, journal={JOURNAL OF ELECTROCERAMICS}, author={Aygun, S and Tan, XL and Maria, JP and Cann, D}, year={2005}, month={Dec}, pages={203–208} }
 @article{losego_jimison_ihlefeld_maria_2005, title={Ferroelectric response from lead zirconate titanate thin films prepared directly on low-resistivity copper substrates}, volume={86}, ISSN={["0003-6951"]}, DOI={10.1063/1.1919388}, abstractNote={We demonstrate films of the well-known ferroelectric lead zirconate titanate (PZT) prepared directly on copper foils by chemical solution deposition (CSD). The films exhibit saturating polarization hysteresis, remanent polarization values of 26μC∕cm2, and permittivities of 800; these properties are comparable to those achieved using semiconductor-grade substrates. The preparation methodology is founded upon an understanding of solution chemistry as opposed to conventional gas-phase ∕ condensed-phase equilibrium approaches. By adopting this technique, base-metal compatibility can be achieved using much lower temperatures, and a broader set of devices can be prepared offering intimate contact with high conductivity, easily patternable, or ferromagnetic metals.}, number={17}, journal={APPLIED PHYSICS LETTERS}, author={Losego, MD and Jimison, LH and Ihlefeld, JF and Maria, JP}, year={2005}, month={Apr} }
 @article{ghosh_laughlin_nath_kingon_steer_maria_2005, title={High Q (Ba, Sr) TiO3 interdigitated capacitors fabricated on low cost polycrystalline alumina substrates with copper metallization}, volume={26}, DOI={10.1002/9780470291252.ch13}, abstractNote={Barium Strontium Titanate (BST) ferroelectric thin films are attractive for radio frequency and microwave applications. However, for many non-military uses, the high cost of conventionally processed devices is a limitingfactor. This high cost stems from the use of single-crystalline sapphire, MgO, or LaAlO 3 substrates and Pt or Au metallization commonly used. Here we present a device process and materials complement offering a low cost alternative. Planar interdigitated capacitors Ba 0 . 7 5 Sr 0 . 2 5 TiO 3 (BST) thin films with chromium/copper top electrodes were fabricated on polycrystalline alumina substrates using a single step photolithographic technique and lift-off. RF magnetron sputtering was used for fabrication of BST thin films while Cu thin films were thermally evaporated The dielectric tunability of the Ba 0 . 7 5 Sr 0 . 2 5 TiO 3 IDCs was 40 % for an applied electric field of 120 kV/cm, which corresponds to 3 μm electrode gap spacing and a 35 volt dc bias. Low frequency (1MHz) loss measurements reveal a dielectric Q ∼ 100 while a device Q of ∼ 30 is obtained at 26 GHz. The reduction of Q between 0.1 and 26 GHz can be attributed to the metallization. Leakage current measurements of the BST planar varactors show current densities of 1.0 x 10 - 6 A / cm 2 for an electric field of 100 kV/cm. These dielectric characteristics (tunability and Q value) are comparable to numerous reports of IDCs with BST films prepared on expensive single crystalline substrates using noble metallization. As such, this technology is significantly less expensive, and amenable to large volume manufacturing.}, number={5}, journal={Ceramic Engineering and Science Proceedings}, author={Ghosh, D. and Laughlin, B. J. and Nath, J. and Kingon, A. I. and Steer, M. B. and Maria, J. P.}, year={2005}, pages={125–132} }
 @article{brewer_wicaksana_maria_kingon_franzen_2005, title={Investigation of the electrical and optical properties of iridium oxide by reflectance FTIR spectroscopy and density functional theory calculations}, volume={313}, ISSN={0301-0104}, url={http://dx.doi.org/10.1016/j.chemphys.2004.11.014}, DOI={10.1016/j.chemphys.2004.11.014}, abstractNote={Variable angle reflectance FTIR spectroscopy was used to investigate the optical properties of iridium oxide thin films deposited on glass substrates in the near-IR spectral region. The reflectance was studied as a function of incident angle and wavenumber for p-polarized radiation. The Drude free-electron model along with the Fresnel equations of reflection were utilized to fit the experimental reflectance FTIR data to determine the plasma frequency and electronic scattering time of this conducting metal oxide thin film. These experimental studies were complemented by density functional theory (DFT) calculations of the electronic and optical properties of iridium oxide. The calculations used the crystal structure of iridium oxide with periodic boundary conditions. These theoretical studies yielded the optical band gap, Fermi energy, charge carrier concentration, effective electron mass, plasma frequency and the conduction band orbital character of iridium oxide. The computed dependence of the optical band gap, Fermi energy, charge carrier concentration and the plasma frequency on compression or expansion of the iridium oxide unit cell was investigated.}, number={1-3}, journal={Chemical Physics}, publisher={Elsevier BV}, author={Brewer, Scott H. and Wicaksana, Dwi and Maria, Jon-Paul and Kingon, Angus I. and Franzen, Stefan}, year={2005}, month={Jun}, pages={25–31} }
 @article{maria_boyette_kingon_ragaglia_stauf_2005, title={Low loss tungsten-based electrode technology for microwave frequency BST varactors}, volume={14}, ISSN={["1385-3449"]}, DOI={10.1007/s10832-005-6587-z}, number={1}, journal={JOURNAL OF ELECTROCERAMICS}, author={Maria, JP and Boyette, BA and Kingon, AI and Ragaglia, C and Stauf, G}, year={2005}, month={Jan}, pages={75–81} }
 @misc{maria_kingon_2005, title={Methods of controlling oxygen partial pressure during annealing of a perovskite dielectric layer}, volume={6,936,301}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Maria, J.-P. and Kingon, A. I.}, year={2005} }
 @misc{maria_kingon_dunn_streiffer_cheek_zhang_savic_2005, title={Multi-layer conductor-dielectric oxide structure}, volume={6,841,080}, number={2005 Jan. 11}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Maria, J.-P. and Kingon, A. and Dunn, G. J. and Streiffer, S. and Cheek, K. and Zhang, M.-X. and Savic, J.}, year={2005} }
 @article{sivasubramani_kim_gnade_wallace_edge_schlom_craft_maria_2005, title={Outdiffusion of La and Al from amorphous LaAlO3 in direct contact with Si(001)}, volume={86}, ISSN={["1077-3118"]}, DOI={10.1063/1.1928316}, abstractNote={We have evaluated the thermal stability of Al2O3/LaAlO3/Si (001) stacks with atomic force microscopy, x-ray diffraction, transmission electron microscopy, and secondary ion mass spectrometry using a back side polishing approach. Crystallization of the amorphous LaAlO3 film was found to occur for rapid thermal anneals (RTA) above 935 °C for 20 s, in flowing N2. Penetration of Al and La into the underlying Si (001) is clearly observed for RTA at or above 950 °C for 20 s in flowing N2.}, number={20}, journal={APPLIED PHYSICS LETTERS}, author={Sivasubramani, P and Kim, MJ and Gnade, BE and Wallace, RM and Edge, LF and Schlom, DG and Craft, HS and Maria, JP}, year={2005}, month={May} }
 @article{laughlin_ihlefeld_maria_2005, title={Preparation of sputtered (Ba-x,Sr1-x)TiO3 thin films directly on copper}, volume={88}, ISSN={["1551-2916"]}, DOI={10.1111/j.1551-2916.2005.00488.x}, abstractNote={ (Ba0.6,Sr0.4)TiO3 (BST) films were deposited on copper foils by radio frequency magnetron sputtering. By the use of controlled pO2 high‐temperature anneals, the films were completely crystallized in the absence of substrate oxidation. X‐ray diffraction and transmission electron microscopy (TEM) revealed an abrupt Cu/BST interface. The deposited BST films exhibit a zero bias permittivity and loss tangent values of 600 and 0.018, respectively. An electrical tunability ratio of 3.5:1 is observed on these metal–insulator–metal devices. Devices show leakage currents of 10−8 A/cm2 at ±10 V/μm, and loss tangents as low as 0.003 in fields approaching 40 V/μm. }, number={9}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Laughlin, B and Ihlefeld, J and Maria, JP}, year={2005}, month={Sep}, pages={2652–2654} }
 @article{victor_nath_ghosh_boyette_maria_steer_kingon_stauf_2004, title={A voltage controlled oscillator using Barium strontium titanate (BST) thin film varactor}, ISBN={["0-7803-8451-2"]}, DOI={10.1109/rawcon.2004.1389079}, abstractNote={Barium strontium titanate (BST) has a field-dependent permittivity and can be used as a dielectric in voltage tunable capacitors or varactors. These BST-based varactors are passive devices and have significantly different properties compared to semiconductor varactors. A voltage tunable oscillator using a BST thin film varactor was designed and characterized. The frequency of oscillation varied from 34.8 MHz to 44.5 MHz (28% tuning) upon application of 7 V tuning voltage. The VCO gain was 1.38 MHz/V and the 2nd harmonic was over 23 dB below the fundamental throughout the tuning range.}, journal={RAWCON: 2004 IEEE RADIO AND WIRELESS CONFERENCE, PROCEEDINGS}, author={Victor, A and Nath, J and Ghosh, D and Boyette, B and Maria, JP and Steer, MB and Kingon, AI and Stauf, GT}, year={2004}, pages={91–94} }
 @article{kim_kingon_maria_croswell_2004, title={Ca-doped lead zirconate titanate thin film capacitors on base metal nickel on copper foil}, volume={19}, ISSN={["0884-2914"]}, DOI={10.1557/jmr.2004.0387}, abstractNote={Ca-doped lead zirconate titanate (52/48) thin film capacitors were prepared on electroless nickel-coated copper foils for embedded capacitor applications. The impact of Ca doping and process parameter variations was studied. Ca addition significantly reduced the temperature coefficient of capacitance. Specifically, the temperature variation was reduced to less than 10% between 300 and 580 K through calcium addition. Optimized capacitance densities and loss tangents were 400 nF/cm2 and 0.02, respectively. Crystallization temperatures of 600 °C yielded these optimized electrical properties, while higher temperatures resulted in interfacial reactions. The influence of oxygen partial pressure during crystallization was also studied. Dielectric properties were sensitive to pO2, with optimal properties occurring in a narrow pO2 window centered about 10−3 Torr. The trends with oxygen pressure were mirrored by changes in phase assemblage. Electrical transport across the dielectric layers was not strongly dependent upon doping level. This insensitivity was attributed to a thin interfacial layer present in all samples. Interface analysis using equivalent circuit analogues showed the nature of the interface to be highly resistive (insulating), rather than semiconducting or conducting.}, number={10}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Kim, T and Kingon, AI and Maria, JP and Croswell, RT}, year={2004}, month={Oct}, pages={2841–2848} }
 @article{lucovsky_maria_phillips_2004, title={Interfacial strain-induced self-organization in semiconductor dielectric gate stacks. II. Strain-relief at internal dielectric interfaces between SiO2 and alternative gate dielectrics}, volume={22}, number={4}, journal={Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures}, author={Lucovsky, G. and Maria, J. P. and Phillips, J. C.}, year={2004}, pages={2097–2104} }
 @misc{maria_kingon_2004, title={Lanthanum oxide-based dielectrics for integrated circuit capacitors}, volume={6,753,567}, number={2004 June 22}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Maria, J.-P. and Kingon, A. I.}, year={2004} }
 @inproceedings{nath_ghosh_maria_steer_kingon_stauf_2004, title={Microwave properties of BST thin film interdigital capacitors on low cost alumina substrates}, ISBN={1580539920}, booktitle={Proceedings of the 34th European Microwave Conference (EuMc), Amsterdam}, publisher={London: Horizon House}, author={Nath, J. and Ghosh, D. and Maria, J.-P. and Steer, M. B. and Kingon, A. I. and Stauf, G. T.}, year={2004}, pages={1497–1500} }
 @article{kim_maria_kingon_streiffer_2003, title={Evaluation of intrinsic and extrinsic contributions to the piezoelectric properties of Pb(Zr1-xTX)O-3 thin films as a function of composition}, volume={93}, ISSN={["0021-8979"]}, DOI={10.1063/1.1566478}, abstractNote={The piezoelectric, dielectric, and ferroelectric properties of highly (111)-textured, 200-nm-thick polycrystalline lead zirconate titanate (PZT) films have been investigated as a function of Zr/Ti ratio. The distinct peak in piezoelectric coefficient at the morphotropic phase boundary found in bulk PZT ceramics is not observed in thin film PZTs. Measurements of the temperature dependence of relative permittivity and the nonlinear behavior of relative permittivity and piezoelectric coefficient suggest that non-180° domain wall motion in these films is negligible, indicating that the extrinsic contribution to the room temperature permittivity is dominated by only 180° domain wall motion. The semiempirical phenomenological equation relating the piezoelectric coefficient to measured polarization and permittivity values is demonstrated to give an excellent description of the piezoelectric behavior in these films, assuming bulk electrostrictive and elastic coefficients. The small deviation between calculated and measured piezoelectric coefficients as well as the dependence of piezoelectric and polarization behavior on the external field, i.e., hysteresis loop, are suggested to be primarily due to backswitching of 180° domains.}, number={9}, journal={JOURNAL OF APPLIED PHYSICS}, author={Kim, DJ and Maria, JP and Kingon, AI and Streiffer, SK}, year={2003}, month={May}, pages={5568–5575} }
 @misc{maria_kingon_2003, title={Lanthanum oxide-based gate dielectrics for integrated circuit field effect transistors}, volume={6,531,354}, number={2003 Mar. 11}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Maria, J.-P. and Kingon, A. I.}, year={2003} }
 @misc{maria_kingon_dunn_streiffer_k._m.-x._savic_2003, title={Multi-layer conductor-dielectric oxide structure}, volume={6,541,137}, number={2003 Apr. 1}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Maria, J.-P and Kingon, A. and Dunn, G. and Streiffer, S.Cheek and K., Zhang and M.-X. and Savic, J.}, year={2003} }
 @article{park_sakhrani_maria_cuomo_teng_muth_ware_rodriguez_nemanich_2003, title={Wavelength-dependent Raman scattering of hydrogenated amorphous silicon carbon with red, green, and blue light excitation}, volume={18}, ISSN={["2044-5326"]}, DOI={10.1557/JMR.2003.0106}, abstractNote={This study presents results of wavelength-dependent Raman scattering from amorphous silicon carbon (a-Si:C:H). The a-Si:C:H films were produced by radio-frequency plasma-enhanced chemical vapor deposition. Prior results with amorphous carbon indicate that laser excitation selectively probes clusters with differing sizes. Our measurements with a-Si:C:H indicate that when using red (632.8 nm), green (514.5 nm), and blue (488.0 nm) excitation, the Raman D and G peaks shift to higher wave numbers as the excitation energy increases. The higher frequency is associated with smaller clusters that are preferentially excited with higher photon energy. It appears that photoluminescence occurs due to radiative recombination from intracluster transitions in Si-alloyed sp2-bonded carbon clusters}, number={4}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Park, M and Sakhrani, V and Maria, JP and Cuomo, JJ and Teng, CW and Muth, JF and Ware, ME and Rodriguez, BJ and Nemanich, RJ}, year={2003}, month={Apr}, pages={768–771} }
 @article{maria_wickaksana_parrette_kingon_2002, title={Crystallization in SiO2-metal oxide alloys}, volume={17}, ISSN={["0884-2914"]}, DOI={10.1557/JMR.2002.0234}, abstractNote={HfO2–SiO2 and La2O3–SiO2 amorphous alloys were prepared, and their crystallization behavior was studied. The results suggest that higher permittivities can be achieved in the La-containing system without devitrification. The crystallization mechanisms between systems are distinctly different, yet observations are consistent with bulk material. Hf-containing materials tend toward phase separation, while La-containing materials tend toward silicate formation. For Hf-containing films, negligible thickness or time dependence was observed. In La-containing films, rapid thermal anneals could improve crystallization resistance, and thickness effects related to interface reactions were observed. These behaviors are discussed in the context of phase diagrams and metastable immiscibility.}, number={7}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Maria, JP and Wickaksana, D and Parrette, J and Kingon, AI}, year={2002}, month={Jul}, pages={1571–1579} }
 @article{asayama_lettieri_zurbuchen_jia_trolier-mckinstry_schlom_streiffer_maria_bu_eom_2002, title={Growth of (103) fiber-textured SrBi2Nb2O9 films on Pt-coated silicon}, volume={80}, ISSN={["1077-3118"]}, DOI={10.1063/1.1463697}, abstractNote={(103) fiber-textured SrBi2Nb2O9 thin films have been grown on Pt-coated Si substrates using a SrRuO3 buffer layer. High-resolution transmission electron microscopy reveals that the fiber texture arises from the local epitaxial growth of (111) SrRuO3 grains on (111) Pt grains and in turn (103) SrBi2Nb2O9 grains on (111) SrRuO3 grains. The films exhibit remanent polarization values of 9 μC/cm2. The uniform grain orientation (fiber texture) should minimize grain-to-grain variations in the remanent polarization, which is important to continued scaling of ferroelectric memory device structures.}, number={13}, journal={APPLIED PHYSICS LETTERS}, author={Asayama, G and Lettieri, J and Zurbuchen, MA and Jia, Y and Trolier-McKinstry, S and Schlom, DG and Streiffer, SK and Maria, JP and Bu, SD and Eom, CB}, year={2002}, month={Apr}, pages={2371–2373} }
 @article{stemmer_chen_keding_maria_wicaksana_kingon_2002, title={Stability of ZrO2 layers on Si (001) during high-temperature anneals under reduced oxygen partial pressures}, volume={92}, ISSN={["1089-7550"]}, DOI={10.1063/1.1481970}, abstractNote={Electron energy-loss spectroscopy and high-resolution transmission electron microscopy were used to investigate ZrO2 layers grown by electron-beam evaporation in a molecular-beam epitaxy system. ZrO2/Si layers were investigated before and after uncapped annealing at 1000 °C under different oxygen partial pressures. The thickness of a SiO2-like, low-dielectric constant layer at the silicon interface was found to depend on the oxygen partial pressure during annealing. At oxygen partial pressures of about 10−4 torr the interfacial silicon oxide thickness increased through oxygen diffusion through the ZrO2 layer and silicon consumption at the interface. At oxygen partial pressures in the range of approximately 10−5 torr, only a thin (1 nm) interfacial silicon oxide layer was present, as required for low-equivalent oxide thicknesses of gate stacks incorporating alternative oxides. Further reduction of the oxygen partial pressures (about 10−7 torr) during annealing resulted in zirconium silicide formation at the interface. ZrO2 films annealed at the optimal partial pressure for a thin interfacial oxide were found to crystallize and contain no silicon. High-resolution analytical capabilities afforded by scanning transmission electron microscopy techniques proved essential in analyzing the stability of these ultrathin layers.}, number={1}, journal={JOURNAL OF APPLIED PHYSICS}, author={Stemmer, S and Chen, ZQ and Keding, R and Maria, JP and Wicaksana, D and Kingon, AI}, year={2002}, month={Jul}, pages={82–86} }
 @article{parker_maria_kingon_2002, title={Temperature and thickness dependent permittivity of (Ba,Sr)TiO3 thin films}, volume={81}, ISSN={["1077-3118"]}, DOI={10.1063/1.1490148}, abstractNote={The temperature and thickness dependence of permittivity of (Ba,Sr)TiO3 has been investigated. The films were deposited by liquid-source metalorganic chemical vapor deposition onto Pt/SiO2/Si, with thicknesses ranging from 15 to 580 nm. The dielectric response was measured from 100 to 520 K. As film thickness decreased, the maximum dielectric constant decreased, the temperature at which the maximum dielectric constant occurred decreased, and the peak in the dielectric constant became more diffuse. A model incorporating a thickness independent interior and a nonferroelectric surface cannot account for these thickness dependencies. To appropriately model these observations a physical model containing thickness and temperature dependent interior and surface components is necessary.}, number={2}, journal={APPLIED PHYSICS LETTERS}, author={Parker, CB and Maria, JP and Kingon, AI}, year={2002}, month={Jul}, pages={340–342} }
 @article{tombak_maria_ayguavives_jin_stauf_kingon_mortazawi_2002, title={Tunable barium strontium titanate thin film capacitors for RF and microwave applications}, volume={12}, ISSN={["1558-1764"]}, DOI={10.1109/7260.975716}, abstractNote={The measurement results for thin film barium strontium titanate (BST) based voltage tunable capacitors intended for RF applications are reported. At 9 V DC, BST capacitors fabricated using MOCVD (metalorganic chemical vapor deposition) method achieved 71% (3.4:1) tunability. The measured device quality factor (Q) for BST varactors is comparable with the device Q for commercially available varactor diodes of similar capacitance. The typical dielectric loss tangent was in the range 0.003-0.009 at VHF. Large signal measurement and modeling results for BST thin film capacitors are also presented.}, number={1}, journal={IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS}, author={Tombak, A and Maria, JP and Ayguavives, F and Jin, Z and Stauf, GT and Kingon, AI and Mortazawi, A}, year={2002}, month={Jan}, pages={3–5} }
 @article{park_maria_cuomo_chang_muth_kolbas_nemanich_carlson_bumgarner_2002, title={X-ray and Raman analyses of GaN produced by ultrahigh-rate magnetron sputter epitaxy}, volume={81}, ISSN={["0003-6951"]}, DOI={10.1063/1.1506781}, abstractNote={Thick films of GaN were studied by x-ray diffraction and Raman spectroscopy. The GaN thick films were deposited on (0001) sapphire using ultrahigh-rate magnetron sputter epitaxy with typical growth rates as high as 10–60 μm/min. The width of the x-ray rocking curve from the (0002) reflection for the sample produced by this technique is ∼300 arcsec, which is unprecedented for GaN produced by a sputtering-type process. Our recent sample shows an x-ray rocking curve width of 240 arcsec. Only allowed modes were observed in the polarized Raman spectra. The background free carrier concentration is lower than 3×1016 cm−3. The phonon lifetime of the Raman E2(2) mode of the sputtered GaN was comparable to that of bulk single crystal GaN grown by sublimation. The quality of the film was uniform across the wafer. The film was thermally stable upon annealing in N2 ambient. The x-ray and Raman analyses revealed that the sputtered GaN films are of high crystalline quality.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Park, M and Maria, JP and Cuomo, JJ and Chang, YC and Muth, JF and Kolbas, RM and Nemanich, RJ and Carlson, E and Bumgarner, J}, year={2002}, month={Sep}, pages={1797–1799} }
 @article{ayguavives_jin_tombak_maria_mortazawi_kingon_2001, title={Contribution of dielectric and metallic losses in RF/microwave tunable varactors using (Ba,Sr)TiO3 thin films}, volume={39}, number={1-4}, journal={Integrated Ferroelectrics}, author={Ayguavives, F. and Jin, Z. and Tombak, A. and Maria, J. P. and Mortazawi, A. and Kingon, A. I.}, year={2001}, pages={1343–1352} }
 @article{baumann_streiffer_bai_ghosh_auciello_thompson_stemmer_rao_eom_xu_et al._2001, title={Epitaxial Pb(Mg1/3Nb2/3)O-3-PbTiO3 thin films grown by MOCVD}, volume={35}, number={1-4}, journal={Integrated Ferroelectrics}, author={Baumann, P. K. and Streiffer, S. K. and Bai, G. R. and Ghosh, K. and Auciello, O. and Thompson, C. and Stemmer, S. and Rao, R. A. and Eom, C. B. and Xu, F. and et al.}, year={2001}, pages={1881–1888} }
 @article{maria_wicaksana_kingon_busch_schulte_garfunkel_gustafsson_2001, title={High temperature stability in lanthanum and zirconia-based gate dielectrics}, volume={90}, ISSN={["0021-8979"]}, DOI={10.1063/1.1391418}, abstractNote={Gate dielectrics composed primarily of lanthana and zirconia were prepared by reactive evaporation. The stability of the layers during high temperature anneals was investigated. By controlling the oxygen partial pressure during heat treatment, lanthana and zirconia films could be protected against reaction with the underlying Si substrate and against the growth of low-ε interface layers. The electrical thickness of the dielectrics could be maintained after a 900 °C exposure. The critical oxygen pressure at 900 °C for low-ε interface formation beneath ZrO2 and La2O3 dielectrics was ∼2e−4 Torr. The interfaces that formed beneath the ZrO2 and La2O3 layers are distinctly different. The sub-ZrO2 interface, influenced primarily by phase separation, tends towards pure SiO2, while the sub-La2O3 interface, influenced primarily by silicate formation, tends towards a La–Si–O alloy. For both materials, reducing the oxygen pressure to values below 10−7 Torr resulted in rapid degradation of the metal oxide. This dielectric degradation is believed to be linked to SiO evaporation. These results suggest that at high temperatures, a window of optimal oxygen partial pressure exists in which the stability of many oxides in contact with silicon can be achieved.}, number={7}, journal={JOURNAL OF APPLIED PHYSICS}, author={Maria, JP and Wicaksana, D and Kingon, AI and Busch, B and Schulte, H and Garfunkel, E and Gustafsson, T}, year={2001}, month={Oct}, pages={3476–3482} }
 @article{maria_cheek_streiffer_kim_dunn_kingon_2001, title={Lead zirconate titanate thin films on base-metal foils: an approach for embedded high-permittivity passive components}, volume={84}, DOI={10.1111/j.1151-2916.2001.tb01029.x}, abstractNote={An approach for embedding high‐permittivity dielectric thin films into glass epoxy laminate packages has been developed. Lead lanthanum zirconate titanate (Pb0.85La0.15(Zr0.52Ti0.48)0.96O3, PLZT) thin films were prepared using chemical solution deposition on nickel‐coated copper foils that were 50 μm thick. Sputter‐deposited nickel top electrodes completed the all‐base‐metal capacitor stack. After high‐temperature nitrogen‐gas crystallization anneals, the PLZT composition showed no signs of reduction, whereas the base‐metal foils remained flexible. The capacitance density was 300–400 nF/cm2, and the loss tangent was 0.01–0.02 over a frequency range of 1–1000 kHz. These properties represent a potential improvement of 2–3 orders of magnitude over currently available embedded capacitor technologies for polymeric packages.}, number={10}, journal={Journal of the American Ceramic Society}, author={Maria, J.-P. and Cheek, K. and Streiffer, S. and Kim, S. H. and Dunn, G. and Kingon, A.}, year={2001}, pages={2436–2438} }
 @article{chen_roeder_kim_maria_kingon_2001, title={Metalorganic chemical vapor deposition Pb(Zr,Ti)O-3 and selected lower electrode structures as a pathway to integrated piezoelectric microelectromechanical systems}, volume={19}, ISSN={["1071-1023"]}, DOI={10.1116/1.1401747}, abstractNote={The actuation mechanism is an important aspect of many micromachined devices. Electrostatic actuation has been the prevailing actuation method due to its relative ease in implementation using conventional silicon microfabrication techniques. Other mechanisms are becoming more accessible to micromachine designs as new materials are introduced into the microfabrication process. Recent progress in nonvolatile memory has led to successful incorporation of Pb(Zr,Ti)O3 (PZT) thin films into microelectronic devices. The present work expands on this area and investigates PZT thin films and electrode/barrier combinations for applications in micromachined devices. Incorporation of PZT thin films into silicon micromachined devices requires electrode systems and deposition techniques that are compatible with silicon microfabrication. In this study, Ir/IrOx and Ir/(Ti,Al)N lower electrode systems were developed to suppress diffusion of reactive species (e.g., Pb) into silicon-based microelectromechanical system devices and to enhance PZT film adhesion. Piezoelectric PZT thin films from 0.3 to 1 μm thick were prepared on silicon wafers with these electrode structures by metalorganic chemical vapor deposition. Hysteresis loops of longitudinal piezoelectric coefficient (d33) were measured by dual-beam interferometry and used to characterize piezoelectric activity in these films. The effective d33 exhibited an apparent dependence on film thickness. d33 values up to 70 pm/V were obtained for 1 μm films, while thinner films exhibited lower d33 values between 54 and 60 pm/V. The dielectric loss (tan δ) was below 2% for most films irrespective of their thickness.}, number={5}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B}, author={Chen, IS and Roeder, JF and Kim, DJ and Maria, JP and Kingon, AI}, year={2001}, pages={1833–1840} }
 @article{stemmer_maria_kingon_2001, title={Structure and stability of La2O3/SiO2 layers on Si(001)}, volume={79}, ISSN={["0003-6951"]}, DOI={10.1063/1.1383268}, abstractNote={High-resolution transmission electron microscopy and electron energy-loss spectroscopy (EELS) were used to investigate La2O3/SiO2/Si structures. The La2O3 layers were deposited on thermal SiO2 on silicon, followed by rapid thermal annealing treatments at 600 °C and 800 °C in a nitrogen ambient. After annealing at 600 °C, the oxide layers were amorphous. After an 800 °C treatment, crystallites appeared in the original La2O3 layer, and the total oxide layer thickness increased by 17%, most likely due to the oxygen diffusion and reaction at the Si/SiO2 interface. EELS, using a 0.2 nm probe, showed that rapid thermal annealing at 600 °C did not cause significant La diffusion into the SiO2 layer, whereas some intermixing was observed at 800 °C. We use the observed microstructures to estimate equivalent oxide thicknesses. The results demonstrate that oxygen partial pressures and initial SiO2 thickness need to be carefully controlled to control SiO2 formation at the Si interface and to achieve target equivalent oxide thickness.}, number={1}, journal={APPLIED PHYSICS LETTERS}, author={Stemmer, S and Maria, JP and Kingon, AI}, year={2001}, month={Jul}, pages={102–104} }
 @article{stauf_ragaglia_roeder_vestyck_maria_ayguavives_kingon_mortazawi_tombak_2001, title={Thick electrodes for high frequency high Q tunable ferroelectric thin film varactors}, volume={39}, DOI={10.1080/10584580108011955}, abstractNote={Abstract Thin film barium strontium titanate (BST) shows great promise for voltage tunable dielectric devices for use at RF and microwave frequencies. An MOCVD process has been developed for production of BST, resulting in films with very low losses (as low as 0.002–0.004) and tunabilities over 50% at low operation voltages. With these values of BST loss, overall device quality factors at RF (100 MHz+) frequencies are primarily limited by losses in the thin metal electrodes, such as Pt, normally used for ferroelectric thin films. The bottom electrode in parallel plate capacitor structures is particularly challenging, since it must provide a good growth surface for BST and be stable at high (>600 °C) growth temperatures in an oxidizing atmosphere yet have high conductivity and compatibility with Si or SiO2/Si substrates. These challenges have previously prevented use of Pt thicknesses over 0.1–0.2 urn. Our solution to this problem, involves combinations of adhesion layers at the Pt/SiO2 interface and embedded stabilization layers to make functioning Pt bottom electrodes as thick as 2 μm. Devices with dielectric Q factors over 150 at 100 MHz (tan δ ∼ 0.006 as measured and modeled by S-parameters) and overall device Q factors over 50 at 30 MHz are described. We have also inserted these devices into tunable filters, achieving tunabilities of 50% and low insertion losses (0.3 dB) at RF frequencies.}, number={1-4}, journal={Integrated Ferroelectrics}, author={Stauf, G. T. and Ragaglia, C. and Roeder, J. F. and Vestyck, D. and Maria, J. P. and Ayguavives, T. and Kingon, A. and Mortazawi, A. and Tombak, A.}, year={2001}, pages={1271–1280} }
 @misc{kingon_maria_streiffer_2000, title={Alternative dielectrics to silicon dioxide for memory and logic devices}, volume={406}, ISSN={["1476-4687"]}, DOI={10.1038/35023243}, abstractNote={The silicon-based microelectronics industry is rapidly approaching a point where device fabrication can no longer be simply scaled to progressively smaller sizes. Technological decisions must now be made that will substantially alter the directions along which silicon devices continue to develop. One such challenge is the need for higher permittivity dielectrics to replace silicon dioxide, the properties of which have hitherto been instrumental to the industry's success. Considerable efforts have already been made to develop replacement dielectrics for dynamic random-access memories. These developments serve to illustrate the magnitude of the now urgent problem of identifying alternatives to silicon dioxide for the gate dielectric in logic devices, such as the ubiquitous field-effect transistor.}, number={6799}, journal={NATURE}, author={Kingon, AI and Maria, JP and Streiffer, SK}, year={2000}, month={Aug}, pages={1032–1038} }
 @article{kim_kim_maria_kingon_streiffer_im_auciello_krauss_2000, title={Influence of Pt heterostructure bottom electrodes on SrBi2Ta2O9 thin film properties}, volume={76}, ISSN={["1077-3118"]}, DOI={10.1063/1.125799}, abstractNote={The properties of SrBi2Ta2O9 (SBT) films, such as remanent polarization and leakage current density, are closely related to the film/electrode interface and surface roughness of the underlying electrode. SBT films grown on stable Pt/TiO2/SiO2/Si and Pt/ZrO2/SiO2/Si substrates exhibit high remanent polarization, low leakage current density, and low voltage saturation as compared to SBT films synthesized on Pt/Ti/SiO2/Si. It is shown that severe diffusion of Ti from the Ti interlayer onto the surface of the Pt bottom electrode and the increased surface roughness of this electrode stack play key roles in degradation of SBT properties.}, number={4}, journal={APPLIED PHYSICS LETTERS}, author={Kim, SH and Kim, DJ and Maria, JP and Kingon, AI and Streiffer, SK and Im, J and Auciello, O and Krauss, AR}, year={2000}, month={Jan}, pages={496–498} }
 @article{maria_mckinstry_trolier-mckinstry_2000, title={Origin of preferential orthorhombic twinning in SrRuO3 epitaxial thin firms}, volume={76}, ISSN={["0003-6951"]}, DOI={10.1063/1.126654}, abstractNote={In order to elucidate the driving forces which promote oriented in-plane crystallographic texture in SrRuO3 thin films deposited on stepped SrTiO3 substrates, a high-temperature x-ray analysis of both SrRuO3 thin films and powders was conducted. Structural phase transitions were found at temperatures near 350 °C and slightly above 600 °C. The transitions are tentatively indexed as orthorhombic to tetragonal and tetragonal to cubic, respectively. These results suggest that SrRuO3 thin films grow with cubic symmetry. As such, film–substrate interfacial characteristics, rather than a preferred growth direction, are believed to determine the orientation of orthorhombic twins.}, number={23}, journal={APPLIED PHYSICS LETTERS}, author={Maria, JP and McKinstry, HL and Trolier-McKinstry, S}, year={2000}, month={Jun}, pages={3382–3384} }
 @article{christman_kim_maiwa_maria_rodriguez_kingon_nemanich_2000, title={Spatial variation of ferroelectric properties in Pb(Zr-0.3, Ti-0.7)O-3 thin films studied by atomic force microscopy}, volume={87}, ISSN={["0021-8979"]}, DOI={10.1063/1.373492}, abstractNote={Imaging of the phase and magnitude of the piezoelectric strain in Pb(Zr0.3, Ti0.7)O3 (PZT) capacitors is performed with an atomic force microscope. The imaging reveals a significant spatial dependence of the ferroelectric properties of both fatigued and unfatigued PZT films. We propose that the variation is related to the domain structure of the PZT. Through the measurement of local piezoelectric hysteresis loops and imaging of the piezoelectric strain, areas are observed in fatigued PZT that exhibit hysteresis loops shifted along the polarization axis. In some regions of fatigued samples, the hysteresis loops are shifted such that both remanent points of the hysteresis curve have the same polarization direction. These results have important implications for the scalability of nonvolatile ferroelectric random access memory to higher device densities.}, number={11}, journal={JOURNAL OF APPLIED PHYSICS}, author={Christman, JA and Kim, SH and Maiwa, H and Maria, JP and Rodriguez, BJ and Kingon, AI and Nemanich, RJ}, year={2000}, month={Jun}, pages={8031–8034} }
 @article{kim_kim_im_streiffer_auciello_maria_kingon_1999, title={Impact of changes in the Pt heterostructure bottom electrodes on the ferroelectric properties of SBT thin films}, volume={26}, DOI={10.1080/10584589908215626}, abstractNote={Abstract The crystallinity and the microstructure of Sr0.8Bi2.3Ta2O9 (SBT) thin films improved with increasing annealing temperature, and strongly influenced the ferroelectric properties. In addition, the properties of SBT films, such as remanent polarization and leakage current density, are closely related to the film/electrode interface and surface roughness of the underlying electrode. SBT films on Pt/TiO2/SiO2/Si and Pt/ZrO2/SiO2/Si substrates exhibited high remanent polarization, low leakage current density, and low voltage saturation as compared to SBT films on Pt/Ti/SiO2/Si substrates. This is deduced to be related to differences in film orientation, electrode roughness, and out-diffusion of Ti onto the surface of the bottom electrode.}, number={1-4}, journal={Integrated Ferroelectrics}, author={Kim, S. H. and Kim, D. J. and Im, J. and Streiffer, S. K. and Auciello, O. and Maria, J. P. and Kingon, A. I.}, year={1999}, pages={955–970} }
 @article{kim_kim_maria_kingon_1999, title={Influences on imprint failure of SrBi2Ta2O9 thin film capacitors}, volume={25}, number={1-4}, journal={Integrated Ferroelectrics}, author={Kim, D. J. and Kim, S. H. and Maria, J. P. and Kingon, A. I.}, year={1999}, pages={691–701} }
 @article{maiwa_maria_christman_kim_streiffer_kingon_1999, title={Measurement and calculation of PZT thin film longitudinal piezoelectric coefficients}, volume={24}, ISSN={["1058-4587"]}, DOI={10.1080/10584589908215586}, abstractNote={The ferroelectric and piezoelectric properties of 2000 {angstrom} thick chemical solution deposited Pb(Zr{sub x}Ti{sub 1{minus}x})O{sub 3} (PZT) thin films were investigated. Several Zr/Ti ratios were studied: 30/70, 50/50 and 65/35, which correspond to tetragonal, near-morphotropic, and rhombohedral symmetries. In all samples, a {l_brace}111{r_brace}-texture is predominant. Longitudinal piezoelectric coefficients and their dc field dependence were measured using the contact AFM method. The expected trend of a maximum piezoelectric coefficient at or near to the MPB was not observed. The composition dependence was small, with the maximum d{sub 33} occurring in the tetragonal material. To explain the results, crystallographic texture and film thickness effects are suggested. Using a modified phenomenological approach, derived electrostrictive coefficients, and experimental data, d{sub 33} values were calculated. Qualitative agreement was observed between the measured and calculated coefficients. Justifications of modifications to the calculations are discussed.}, number={1-4}, journal={INTEGRATED FERROELECTRICS}, author={Maiwa, H and Maria, JP and Christman, JA and Kim, SH and Streiffer, K and Kingon, AI}, year={1999}, pages={139–146} }
 @article{maiwa_christman_kim_kim_maria_chen_streiffer_kingon_1999, title={Measurement of piezoelectric displacements of Pb(Zr, Ti)O-3 thin films using a double-beam interferometer}, volume={38}, ISSN={["0021-4922"]}, DOI={10.1143/jjap.38.5402}, abstractNote={ 
  The double-beam interferometric method is applied to measure the field-induced  
  displacement of Pb(Zr, Ti)O3 thin films. The dc electric field dependence of the  
  longitudinal piezoelectric coefficient (d
                  33) response of Pb(Zr, Ti)O3 thin films deposited  
  by metal organic chemical vapor deposition (MOCVD) was measured. Experimental d
                  33  
  values were compared with coefficients calculated using a phenomenological approach  
  and bulk parameters. Qualitative agreement was obtained between measured and  
  calculated coefficients. 
  }, number={9B}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS}, author={Maiwa, H and Christman, JA and Kim, SH and Kim, DJ and Maria, JP and Chen, B and Streiffer, SK and Kingon, AI}, year={1999}, month={Sep}, pages={5402–5405} }