@article{pham_gai_rochester_dycus_lebeau_manga_corral_2023, title={Thermodynamic assessment within the Zr-B-C-O quaternary system}, ISSN={["1551-2916"]}, DOI={10.1111/jace.18958}, abstractNote={Abstract}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Pham, David and Gai, Fangyuan and Rochester, Jacob and Dycus, Joseph H. and LeBeau, James M. and Manga, Venkateswara Rao and Corral, Erica L.}, year={2023}, month={Jan} }
 @article{zhang_penn_wysocki_zhang_loosdrecht_kornblum_lebeau_lindfors-vrejoiu_kumah_2022, title={Thickness and temperature dependence of the atomic-scale structure of SrRuO3 thin films}, volume={10}, ISSN={["2166-532X"]}, url={https://doi.org/10.1063/5.0087791}, DOI={10.1063/5.0087791}, abstractNote={The temperature-dependent layer-resolved structure of 3 to 44 unit cell thick SrRuO3 (SRO) films grown on Nb-doped SrTiO3 substrates is investigated using a combination of high-resolution synchrotron x-ray diffraction and high-resolution electron microscopy to understand the role that structural distortions play in suppressing ferromagnetism in ultra-thin SRO films. The oxygen octahedral tilts and rotations and Sr displacements characteristic of the bulk orthorhombic phase are found to be strongly dependent on temperature, the film thickness, and the distance away from the film–substrate interface. For thicknesses, t, above the critical thickness for ferromagnetism (t > 3 uc), the orthorhombic distortions decrease with increasing temperature above TC. Below TC, the structure of the films remains constant due to the magneto-structural coupling observed in bulk SRO. The orthorhombic distortions are found to be suppressed in the 2–3 interfacial layers due to structural coupling with the SrTiO3 substrate and correlate with the critical thickness for ferromagnetism in uncapped SRO films.}, number={5}, journal={APL MATERIALS}, author={Zhang, Xuanyi and Penn, Aubrey N. and Wysocki, Lena and Zhang, Zhan and Loosdrecht, Paul H. M. and Kornblum, Lior and LeBeau, James M. and Lindfors-Vrejoiu, Ionela and Kumah, Divine P.}, year={2022}, month={May} }
 @article{miller_cabral_dickey_lebeau_reich_2021, title={Accounting for Location Measurement Error in Imaging Data With Application to Atomic Resolution Images of Crystalline Materials}, volume={4}, ISSN={["1537-2723"]}, url={https://app.dimensions.ai/details/publication/pub.1136536111}, DOI={10.1080/00401706.2021.1905070}, abstractNote={Abstract Scientists use imaging to identify objects of interest and infer properties of these objects. The locations of these objects are often measured with error, which when ignored leads to biased parameter estimates and inflated variance. Current measurement error methods require an estimate or knowledge of the measurement error variance to correct these estimates, which may not be available. Instead, we create a spatial Bayesian hierarchical model that treats the locations as parameters, using the image itself to incorporate positional uncertainty. We lower the computational burden by approximating the likelihood using a noncontiguous block design around the object locations. We use this model to quantify the relationship between the intensity and displacement of hundreds of atom columns in crystal structures directly imaged via scanning transmission electron microscopy (STEM). Atomic displacements are related to important phenomena such as piezoelectricity, a property useful for engineering applications like ultrasound. Quantifying the sign and magnitude of this relationship will help materials scientists more precisely design materials with improved piezoelectricity. A simulation study confirms our method corrects bias in the estimate of the parameter of interest and drastically improves coverage in high noise scenarios compared to non-measurement error models.}, number={1}, journal={TECHNOMETRICS}, author={Miller, Matthew J. and Cabral, Matthew J. and Dickey, Elizabeth C. and LeBeau, James M. and Reich, Brian J.}, year={2021}, month={Apr} }
 @article{nozariasbmarz_dycus_cabral_flack_krasinski_lebeau_vashaee_2021, title={Efficient self-powered wearable electronic systems enabled by microwave processed thermoelectric materials}, volume={283}, ISSN={["1872-9118"]}, DOI={10.1016/j.apenergy.2020.116211}, abstractNote={The integrated body sensor networks are expected to dominate the future of healthcare, making a critical paradigm shift that will support people in the comfort and security of their own homes. Thermoelectric generators, in this regard, can play a crucial role as they can steadily generate electricity from body heat and enable self-powered wearable or implantable medical, health, and sports devices. This work provides a comprehensive analysis of the operation and the optimization of wearable thermoelectric generators under different human body conditions. Thermoelectric design principles, wearable system considerations, and a novel method to synthesize the materials specially designed for body heat harvesting are presented. The limitations of the materials and systems for wearable applications are deliberated in detail, and the feasibility of eliminating the heatsink for enhancing body comfort is examined. N-type Bi2Te3-xSex was synthesized using a novel approach based on field-induced decrystallization by microwave radiation to achieve the optimum properties. This method resulted in amorphous-crystalline nanocomposites with simultaneously large thermopower and small thermal conductivity around the body temperature. Thermoelectric generators were fabricated from the optimized materials and packaged in flexible elastomers. The devices generated up to 150% higher voltage and 600% more power on the body compared to the commercial ones and, so far, are the best in class for body heat harvesting in wearable applications.}, journal={APPLIED ENERGY}, author={Nozariasbmarz, Amin and Dycus, J. Houston and Cabral, Matthew J. and Flack, Chloe M. and Krasinski, Jerzy S. and LeBeau, James M. and Vashaee, Daryoosh}, year={2021}, month={Feb} }
 @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{gai_dycus_lebeau_walker_corral_2021, title={Instantaneous nanowelding of ultra-high temperature ceramics for hypersonics}, ISSN={["1551-2916"]}, DOI={10.1111/jace.17866}, abstractNote={Abstract}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Gai, Fangyuan and Dycus, Joseph Houston and LeBeau, James M. and Walker, Luke S. and Corral, Erica L.}, year={2021}, month={May} }
 @article{mirrielees_dycus_baker_reddy_collazo_sitar_lebeau_irving_2021, title={Native oxide reconstructions on AlN and GaN (0001) surfaces}, volume={129}, ISSN={["1089-7550"]}, DOI={10.1063/5.0048820}, abstractNote={Properties of AlN/GaN surfaces are important for realizing the tunability of devices, as the presence of surface states contributes to Fermi level pinning. This pinning can influence the performance of high electron mobility transistors and is also important for passivation of the surface when developing high-power electronic devices. It is widely understood that both AlN and GaN surfaces oxidize. Since there are many possible reconstructions for each surface, it is a challenge to identify the relevant surface reconstructions in advance of a detailed simulation. Because of this, different approaches are often employed to down select initial structures to reduce the computational load. These approaches usually rely on either electron counting rules or oxide stoichiometry, as both of these models tend to lead to structures that are energetically favorable. Here we explore models from these approaches but also explore a reconstruction of the (0001) surface directly observed using scanning transmission electron microscopy with predictive density functional theory simulations. Two compositions of the observed surface reconstruction—one which obeys oxide stoichiometry and one which is cation deficient and obeys electron counting—are compared to reconstructions from the previous work. Furthermore, surface states are directly calculated using hybrid exchange-correlation functionals that correct for the underestimation of the bandgaps in AlN and GaN and improve the predicted positions of surface states within the gap. It is found that cation deficiency in the observed reconstruction yields surface states consistent with the experiment. Based on all of these results, we provide insight into the observed properties of oxidized AlGaN surfaces.}, number={19}, journal={JOURNAL OF APPLIED PHYSICS}, author={Mirrielees, Kelsey J. and Dycus, J. Houston and Baker, Jonathon N. and Reddy, Pramod and Collazo, Ramon and Sitar, Zlatko and LeBeau, James M. and Irving, Douglas L.}, year={2021}, month={May} }
 @article{hauwiller_stowe_eldred_mita_collazo_sitar_lebeau_2020, title={Cathodoluminescence of silicon doped aluminum nitride with scanning transmission electron microscopy}, volume={8}, ISSN={["2166-532X"]}, DOI={10.1063/5.0019863}, abstractNote={Here, we apply cathodoluminescence in scanning transmission electron microscopy to infer the influence of dislocation strain fields on the formation of point defect complexes in Si doped AlN. In addition to identifying non-radiative recombination centers, tracking Si related defect emission energies reveals a red-shift at threading dislocations. We discuss these results in the context of multiple Si-vacancy defect complexes that can form and the influence of local strain on their formation energies. By correlating the electronic and structural properties at the nanoscale, cathodoluminescence elucidates the inhomogeneity of defect complexes in Si doped AlN and offers the potential for strain engineering to control the defect energy formation landscape.}, number={9}, journal={APL MATERIALS}, author={Hauwiller, Matthew R. and Stowe, David and Eldred, Timothy B. and Mita, Seiji and Collazo, Ramon and Sitar, Zlatko and LeBeau, James}, year={2020}, month={Sep} }
 @article{chen_hauwiller_kumar_penn_lebeau_2020, title={Expanding the Dimensions of a Small, Two-Dimensional Diffraction Detector}, volume={26}, ISSN={["1435-8115"]}, DOI={10.1017/S1431927620024277}, abstractNote={Abstract}, number={5}, journal={MICROSCOPY AND MICROANALYSIS}, author={Chen, Xi and Hauwiller, Matthew R. and Kumar, Abinash and Penn, Aubrey N. and LeBeau, James M.}, year={2020}, month={Oct}, pages={938–943} }
 @article{jo_li_singh_kumar_frisone_lebeau_jaramillo_2020, title={Formation of large-area MoS2 thin films by oxygen-catalyzed sulfurization of Mo thin films}, volume={38}, ISSN={["1520-8559"]}, DOI={10.1116/1.5132748}, abstractNote={While transition metal dichalcogenide (TMD) thin films are most commonly synthesized by vapor transport using solid metal oxide precursors, directly converting metal thin films to TMDs may be more scalable and controllable, e.g., to enable large-area coating by vacuum deposition. The thermodynamics are favorable for MoS2 formation from Mo in sulfur-rich environments, but sulfurization tends to be slow and the product is highly dependent on the chemical pathway taken. Here, the authors report on the role of trace oxygen gas (O2) for the sulfurization of Mo films. They study the formation of MoS2 from Mo films in H2S vapor, between 350 and 500 °C and with varying levels of O2. They find that the presence of trace levels of O2 accelerates the crystallization of MoS2 and affects the layer orientation, without changing the kinetics of mass transport or the final film composition. O2 acts as a catalyst to promote the crystallization of MoS2 at lower temperatures than otherwise possible. These results provide new insights into the growth of MoS2 by sulfurization and suggest that introducing an appropriate catalyst during chalcogenide phase formation could enable new processes for making homogeneous, large-area MoS2 films at low processing temperature on a variety of substrates.}, number={1}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Jo, Seong Soon and Li, Yifei and Singh, Akshay and Kumar, Abinash and Frisone, Sam and LeBeau, James M. and Jaramillo, Rafael}, year={2020}, month={Jan} }
 @article{eldred_abdelhamid_reynolds_el-masry_lebeau_bedair_2020, title={Observing relaxation in device quality InGaN templates by TEM techniques}, volume={116}, ISSN={["1077-3118"]}, DOI={10.1063/1.5139269}, abstractNote={Device quality InGaN templates are synthesized using the semibulk (SB) approach. The approach maintains the film's 2D growth and avoids the formation of indium-metal inclusions. The strain relaxation processes of the grown InxGa1−xN templates are accompanied by variations in the indium content (x) and lattice parameters (a and c) across the InGaN template's thickness as the residual strain is continuously decreasing. This strain and lattice parameters' variation creates difficulties in applying standard x-ray Diffraction (XRD) and Reciprocal Space mapping (RSM) techniques to estimate the residual strain and the degree of the elastic strain relaxation. We used high-resolution High-angle annular dark-field scanning transmission electron microscopy and Energy-dispersive x-ray spectroscopy (EDS) to monitor the variations of the indium content, lattice parameters, and strain relaxation across the growing InxGa1−xN templates. We show that strain relaxation takes place by V-pit defect formation. Some of these V-pits are refilled by the GaN interlayers in the InxGa1−xN SB templates, while others propagate to the template surface. We present an alternative approach combining photoluminescence (PL) and EDS for estimating the degree of strain relaxation in these InxGa1−xN templates. The values obtained for the degree of relaxation estimated from TEM studies and PL measurements are within reasonable agreement in this study. Device quality InxGa1−xN templates with x ∼ 0.08, with a degree of relaxation higher than 70%, are achieved.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Eldred, Tim B. and Abdelhamid, Mostafa and Reynolds, J. G. and El-Masry, N. A. and LeBeau, James M. and Bedair, S. M.}, year={2020}, month={Mar} }
 @article{nozariasbmarz_suarez_dycus_cabral_lebeau_ozturk_vashaee_2020, title={Thermoelectric generators for wearable body heat harvesting: Material and device concurrent optimization}, volume={67}, ISSN={["2211-3282"]}, DOI={10.1016/j.nanoen.2019.104265}, abstractNote={Body heat harvesting systems based on thermoelectric generators (TEGs) can play a significant role in wearable electronics intended for continuous, long-term health monitoring. However, to date, the harvested power density from the body using TEGs is limited to a few micro-watts per square centimeter, which is not sufficient to turn on many wearables. The thermoelectric materials research has been mainly focused on enhancing the single parameter zT, which is insufficient to meet the requirements for wearable applications. To develop TEGs that work effectively in wearable devices, one has to consider the material, device, and system requirements concurrently. Due to the lack of an efficient heatsink and the skin thermal resistance, a key challenge to achieving this goal is to design systems that maximize the temperature differential across the TEG while not compromising the body comfort. This requires favoring approaches that deliver the largest possible device thermal resistance relative to the external parasitic resistances. Therefore, materials with low thermal conductivity are critically important to maximize the temperature gradient. Also, to achieve a high boost converter efficiency, wearable TEGs need to have the highest possible output voltage, which calls for a high Seebeck coefficient. At the device level, dimensions of the legs (length versus the base area) and fill factor are both critical parameters to ensure that the parasitic thermal resistances are again negligible compared to the resistance of the module itself. In this study, the concurrent impact of material and device parameters on the efficiency of wearable TEGs is considered. Nanocomposite thermoelectric materials based on bismuth telluride alloys were synthesized using microwave processing and optimized to meet the requirements of wearable TEGs. Microwave energy decrystallized the material leading to a strong reduction of the thermal conductivity while maintaining a high zT at the body temperature. A comprehensive quasi-3D analytical model was developed and used to optimize the material and device parameters. The nanocomposite TEG produced 44 μW/cm2 under no air flow condition, and 156.5 μW/cm2 under airflow. In comparison to commercial TEGs tested under similar conditions, the nanocomposite based TEGs exhibited 4–7 times higher power density on the human body depending on the convective cooling conditions.}, journal={NANO ENERGY}, author={Nozariasbmarz, Amin and Suarez, Francisco and Dycus, J. Houston and Cabral, Matthew J. and LeBeau, James M. and Ozturk, Mehmet C. and Vashaee, Daryoosh}, year={2020}, month={Jan} }
 @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{koohfar_georgescu_penn_lebeau_arenholz_kumah_2019, title={Confinement of magnetism in atomically thin La0.7Sr0.3CrO3/La0.7Sr0.3MnO3 heterostructures}, volume={4}, ISSN={2397-4648}, url={http://dx.doi.org/10.1038/s41535-019-0164-1}, DOI={10.1038/s41535-019-0164-1}, abstractNote={Abstract}, number={1}, journal={npj Quantum Materials}, publisher={Springer Science and Business Media LLC}, author={Koohfar, Sanaz and Georgescu, Alexandru B. and Penn, Aubrey N. and LeBeau, James M. and Arenholz, Elke and Kumah, Divine P.}, year={2019}, month={May} }
 @article{trappen_grutter_huang_penn_mottaghi_yousefi_haertter_kumari_lebeau_kirby_et al._2019, title={Effect of oxygen stoichiometry on the magnetization profiles and negative magnetization in LSMO thin films}, volume={126}, ISSN={["1089-7550"]}, DOI={10.1063/1.5111858}, abstractNote={The depth-dependent magnetization in thin film oxygen stoichiometric and oxygen-deficient La0.7Sr0.3MnO3 is investigated by using polarized neutron reflectivity and DC bulk magnetometry. The polarized neutron reflectivity results reveal that the stoichiometric sample shows enhanced interfacial magnetization relative to the rest of the film. The oxygen-deficient sample exhibits a reduced average magnetization from the optimized recipe. Both films show regions of suppressed magnetization at the surface regardless of the growth pressure. The oxygen stoichiometric film does not show an interfacial dead layer, whereas the oxygen-deficient film exhibits a dead layer whose thickness changes with temperature. At a low applied field, we observe striking differences in the depth dependence of the magnetic ordering, with the oxygen-deficient film exhibiting exchange spring behavior, while the stoichiometric film shows a constant magnetization direction across the film. These results suggest that the incorporation of oxygen vacancies during growth leads to an accumulation of vacancies at the interface, which is enhanced at higher temperature due to increased oxygen mobility, creating a region of reduced magnetism that couples to the rest of the film. These results offer insight into the complex behavior and role of oxygen vacancies in the magnetism of these systems. Additionally, the study reveals further details of the negative magnetization in La0.7Sr0.3MnO3 reported in previous studies, which are discussed here.}, number={10}, journal={JOURNAL OF APPLIED PHYSICS}, author={Trappen, Robbyn and Grutter, Alexander J. and Huang, Chih-Yeh and Penn, Aubrey and Mottaghi, Navid and Yousefi, Saeed and Haertter, Allison and Kumari, Shalini and LeBeau, James and Kirby, Brian J. and et al.}, year={2019}, month={Sep} }
 @article{milleville_chen_lennon_cleveland_kumar_zhang_bork_tessier_lebeau_chase_et al._2019, title={Engineering Efficient Photon Upconversion in Semiconductor Heterostructures}, volume={13}, ISSN={["1936-086X"]}, DOI={10.1021/acsnano.8b07062}, abstractNote={Photon upconversion is a photophysical process in which two low-energy photons are converted into one high-energy photon. Photon upconversion has broad appeal for a range of applications from biomedical imaging and targeted drug release to solar energy harvesting. Current upconversion nanosystems, including lanthanide-doped nanocrystals and triplet-triplet annihilation molecules, have achieved upconversion quantum yields on the order of 10-30%. However, the performance of these materials is hampered by inherently narrow absorption cross sections and fixed energy levels originating in atomic, ionic, or molecular states. Semiconductors, on the other hand, have inherently wide absorption cross sections. Moreover, recent advances enable the synthesis of colloidal semiconductor nanoparticles with complex heterostructures that can control band alignments and tune optical properties. We synthesize and characterize a three-component heterostructure that successfully upconverts photons under continuous-wave illumination and solar-relevant photon fluxes. The heterostructure is composed of two cadmium selenide quantum dots (QDs), an absorber and emitter, spatially separated by a cadmium sulfide nanorod (NR). We demonstrate that the principles of semiconductor heterostructure engineering can be applied to engineer improved upconversion efficiency. We first eliminate electron trap states near the surface of the absorbing QD and then tailor the band gap of the NR such that charge carriers are funneled to the emitting QD. When combined, these two changes result in a 100-fold improvement in photon upconversion performance.}, number={1}, journal={ACS NANO}, author={Milleville, Christopher C. and Chen, Eric Y. and Lennon, Kyle R. and Cleveland, Jill M. and Kumar, Abinash and Zhang, Jing and Bork, James A. and Tessier, Ansel and LeBeau, James M. and Chase, D. Bruce and et al.}, year={2019}, month={Jan}, pages={489–497} }
 @article{li_cabral_xu_cheng_dickey_lebeau_wang_luo_taylor_hackenberger_et al._2019, title={Giant piezoelectricity of Sm-doped Pb(Mg1/3Nb2/3)O-3-PbTiO3 single crystals}, volume={364}, ISSN={["1095-9203"]}, url={https://doi.org/10.1126/science.aaw2781}, DOI={10.1126/science.aaw2781}, abstractNote={Samarium supersensors}, number={6437}, journal={SCIENCE}, publisher={American Association for the Advancement of Science (AAAS)}, author={Li, Fei and Cabral, Matthew J. and Xu, Bin and Cheng, Zhenxiang and Dickey, Elizabeth C. and LeBeau, James M. and Wang, Jianli and Luo, Jun and Taylor, Samuel and Hackenberger, Wesley and et al.}, year={2019}, month={Apr}, pages={264-+} }
 @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{matveyev_mikheev_negrov_zarubin_kumar_grimley_lebeau_gloskovskii_tsymbal_zenkevich_2019, title={Polarization-dependent electric potential distribution across nanoscale ferroelectric Hf0.5Zr0.5O2 in functional memory capacitors}, volume={11}, ISSN={["2040-3372"]}, DOI={10.1039/c9nr05904k}, abstractNote={Using standing-waves in HAXPES technique, we reveal non-linear electrostatic potential profile across nanoscale ferroelectric (FE) HfZrO4 layer in memory capacitors for both polarization directions, implying the drift of non-FE charges at interfaces.}, number={42}, journal={NANOSCALE}, author={Matveyev, Yury and Mikheev, Vitalii and Negrov, Dmitry and Zarubin, Sergei and Kumar, Abinash and Grimley, Everett D. and LeBeau, James M. and Gloskovskii, Andrei and Tsymbal, Evgeny Y. and Zenkevich, Andrei}, year={2019}, month={Nov}, pages={19814–19822} }
 @article{dycus_washiyama_eldred_guan_kirste_mita_sitar_collazo_lebeau_2019, title={The role of transient surface morphology on composition control in AlGaN layers and wells}, volume={114}, ISSN={["1077-3118"]}, DOI={10.1063/1.5063933}, abstractNote={The mechanisms governing “compositional pulling” during the growth of AlxGa1−xN wells are investigated. Gallium-rich AlxGa1−xN wells grown on high dislocation density AlN/sapphire templates exhibit asymmetric and diffuse composition profiles, while those grown on low dislocation density native AlN substrates do not. Furthermore, strain in all AlxGa1−xN wells is found to be pseudomorphic, ruling it out as the dominating driving force. Rather, the high threading dislocation density of the AlN template is considered to play the defining role. We propose that a transient surface morphology is introduced during dislocation mediated spiral growth, which, in conjunction with process supersaturation, determines the Ga incorporation. These findings provide insights into compositional pulling in high Ga content AlxGa1−xN grown on AlN and provide a route to grow thicker wells with very abrupt interfaces on native AlN substrates.}, number={3}, journal={APPLIED PHYSICS LETTERS}, author={Dycus, J. Houston and Washiyama, Shun and Eldred, Tim B. and Guan, Yan and Kirste, Ronny and Mita, Seiji and Sitar, Zlatko and Collazo, Ramon and LeBeau, James M.}, year={2019}, month={Jan} }
 @article{pham_dycus_lebeau_manga_muralidharan_corral_2019, title={Thermochemical model on the carbothermal reduction of oxides during spark plasma sintering of zirconium diboride}, volume={102}, ISSN={["1551-2916"]}, DOI={10.1111/jace.15911}, abstractNote={Abstract}, number={2}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Pham, David and Dycus, Joseph H. and LeBeau, James M. and Manga, Venkateswara R. and Muralidharan, Krishna and Corral, Erica L.}, year={2019}, month={Feb}, pages={757–767} }
 @article{dhall_cabral_kumar_lebeau_2018, title={A Novel Template for in-situ Microscopy to Reveal Ferroelectric Switching Mechanisms Across Length Scales}, volume={24}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927618009522}, DOI={10.1017/S1431927618009522}, abstractNote={When polar materials are subjected to large external electric fields, they often undergo structural changes, which can give them their useful physical properties (such as phase change materials, or ferroelectrics), or at times lead to device failure (such as breakdown). In-situ microscopy offers the ideal approach to study the response of such polar materials to external electric fields. Efforts in this direction are, however, often plagued by challenges of sample preparation. The use of focused ion-beam milling, in particular, tends to degrade device properties, create sample damage, and the unwanted spray of excess Ga can lead to electrical shorts. Furthermore, creating an electron transparent sample, which accurately represents real-world devices is not trivial.}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Dhall, Rohan and Cabral, Matthew and Kumar, Abinash and LeBeau, James M.}, year={2018}, month={Aug}, pages={1808–1809} }
 @article{xu_lebeau_2018, title={A deep convolutional neural network to analyze position averaged convergent beam electron diffraction patterns}, volume={188}, ISSN={["1879-2723"]}, DOI={10.1016/j.ultramic.2018.03.004}, abstractNote={We establish a series of deep convolutional neural networks to automatically analyze position averaged convergent beam electron diffraction patterns. The networks first calibrate the zero-order disk size, center position, and rotation without the need for pretreating the data. With the aligned data, additional networks then measure the sample thickness and tilt. The performance of the network is explored as a function of a variety of variables including thickness, tilt, and dose. A methodology to explore the response of the neural network to various pattern features is also presented. Processing patterns at a rate of ∼ 0.1 s/pattern, the network is shown to be orders of magnitude faster than a brute force method while maintaining accuracy. The approach is thus suitable for automatically processing big, 4D STEM data. We also discuss the generality of the method to other materials/orientations as well as a hybrid approach that combines the features of the neural network with least squares fitting for even more robust analysis. The source code is available at https://github.com/subangstrom/DeepDiffraction.}, journal={ULTRAMICROSCOPY}, author={Xu, W. and LeBeau, J. M.}, year={2018}, month={May}, pages={59–69} }
 @article{lebeau_dickey_augustyn_hesterberg_brown_2018, title={Acquisition of a microscope for in situ studies of hard and soft matter}, volume={24}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S143192761801214X}, DOI={10.1017/S143192761801214X}, abstractNote={,}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={LeBeau, James M. and Dickey, Elizabeth C. and Augustyn, Veronica and Hesterberg, Dean L. and Brown, Ashley C.}, year={2018}, month={Aug}, pages={2332–2333} }
 @article{fengler_nigon_muralt_grimley_sang_sessi_hentschel_lebeau_mikolajick_schroeder_2018, title={Analysis of Performance Instabilities of Hafnia-Based Ferroelectrics Using Modulus Spectroscopy and Thermally Stimulated Depolarization Currents}, volume={4}, ISSN={["2199-160X"]}, DOI={10.1002/aelm.201700547}, abstractNote={Abstract}, number={3}, journal={ADVANCED ELECTRONIC MATERIALS}, author={Fengler, Franz P. G. and Nigon, Robin and Muralt, Paul and Grimley, Everett D. and Sang, Xiahan and Sessi, Violetta and Hentschel, Rico and LeBeau, James M. and Mikolajick, Thomas and Schroeder, Uwe}, year={2018}, month={Mar} }
 @article{grimley_schenk_mikolajick_schroeder_lebeau_2018, title={Atomic Structure of Domain and Interphase Boundaries in Ferroelectric HfO2}, volume={5}, ISSN={2196-7350}, url={http://dx.doi.org/10.1002/ADMI.201701258}, DOI={10.1002/ADMI.201701258}, abstractNote={Abstract}, number={5}, journal={Advanced Materials Interfaces}, publisher={Wiley}, author={Grimley, Everett D. and Schenk, Tony and Mikolajick, Thomas and Schroeder, Uwe and LeBeau, James M.}, year={2018}, month={Jan}, pages={1701258} }
 @article{boyd_dhall_lebeau_augustyn_2018, title={Charge storage mechanism and degradation of P2-type sodium transition metal oxides in aqueous electrolytes}, volume={6}, ISSN={["2050-7496"]}, DOI={10.1039/c8ta08367c}, abstractNote={P2-type sodium transition metal oxides undergo water-driven structural changes that strongly affect electrochemical charge storage in aqueous electrolytes.}, number={44}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Boyd, Shelby and Dhall, Rohan and LeBeau, James M. and Augustyn, Veronica}, year={2018}, month={Nov}, pages={22266–22276} }
 @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{penn_kumar_trappen_cabrera_holcomb_lebeau_2018, title={Depth Dependence Investigation of Manganese Charge State in Oxygen-deficient LSMO Thin Films}, volume={24}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927618007869}, DOI={10.1017/S1431927618007869}, abstractNote={Lanthanum strontium manganite (LSMO) complex oxide thin films are of interest for applications with colossal magnetoresistance, half-metallic behavior, high conductivity, and room temperature ferromagnetism. Additionally, LSMO thin films exhibit charge redistribution when interfaced with other complex oxides such as strontium titanate [1, 2]. A major limiting factor of these metal oxides, however, is that they lose magnetic behavior and metallicity in exceedingly thin films due to electronic and structural reconstructions [3]. Near the interfaces, for example, the MnO 6 octahedra in these perovskites are found to distort. Furthermore, a mixture of Mn 2+ , 3+ and 4+ charge states exist in LSMO, and it is widely observed that the oxidation state decreases exponentially as the interface is approached [4]. Because dead layers and Mn valence reduction both occur within a several unit cell range, extracting spatially resolved electronic and structural information is of utmost importance for identifying mechanisms leading to degraded properties. In this presentation, we will report on the variation of Mn charge state and local crystallographic distortion as a function of oxygen deficiency. The La 0.33 Sr 0.67 MnO 3 films, grown on SrTiO 3 by pulsed laser deposition [2], are found to require careful sample preparation, particularly during Ar + ion milling [6] to capture the true electronic structure of the interface. To investigate local strain, we will present results from Revolving STEM (RevSTEM), to determine differences of the interface structure and to quantify octahedral distortion [7]}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Penn, Aubrey N. and Kumar, Abinash and Trappen, Robbyn and Cabrera, Guerau and Holcomb, Mikel B. and LeBeau, James M.}, year={2018}, month={Aug}, pages={1476–1477} }
 @article{broderick_kumar_oni_lebeau_sinnott_rajan_2018, title={Discovering chemical site occupancy- modulus correlations in Ni based intermetallics via statistical learning methods}, volume={14}, ISSN={2352-2143}, url={http://dx.doi.org/10.1016/J.COCOM.2017.11.001}, DOI={10.1016/J.COCOM.2017.11.001}, abstractNote={We show how one may extract spectral features from the density of states (DOS) of L12-Ni3Al alloys that can serve as signatures or electronic “fingerprints” which capture the correlation between site occupancy of dopants and elastic properties. Based on this correlation, we have developed a computational approach for rapidly identifying the impact of the selection of dopant chemistries on bulk moduli of intermetallics. Our results show for example that Cr preferentially occupies the Al site in Ni3Al which is confirmed by scanning transmission electron microscopy (STEM) energy dispersed X-ray spectroscopy (EDS) analysis. We further show that this preference is due to a sensitivity of Cr to the DOS at −1.7 and 0.2 eV relative to the Fermi energy. In terms of similarity in chemistry-property correlations, we find Cr has a similar effect to Ce when occupying an Al site, while Cr occupying a Ni site has similar correlation as La on a Ni site. This logic can be utilized in targeted design of new alloy chemistries based on similar property correlations and for targeted DOS modification.}, journal={Computational Condensed Matter}, publisher={Elsevier BV}, author={Broderick, Scott R. and Kumar, Aakash and Oni, Adedapo A. and LeBeau, James M. and Sinnott, Susan B. and Rajan, Krishna}, year={2018}, month={Mar}, pages={8–14} }
 @article{trappen_garcia-castro_tra_huang_ibarra-hernandez_fitch_singh_zhou_cabrera_chu_et al._2018, title={Electrostatic potential and valence modulation in La0.7Sr0.3MnO3 thin films}, volume={8}, ISSN={["2045-2322"]}, DOI={10.1038/s41598-018-32701-x}, abstractNote={Abstract}, journal={SCIENTIFIC REPORTS}, author={Trappen, Robbyn and Garcia-Castro, A. C. and Tra, Vu Thanh and Huang, Chih-Yeh and Ibarra-Hernandez, Wilfredo and Fitch, James and Singh, Sobhit and Zhou, Jinling and Cabrera, Guerau and Chu, Ying-Hao and et al.}, year={2018}, month={Sep} }
 @article{kumar_chang_grimley_chen_lebeau_2018, title={Extracting Thickness and Tilt From 4D-STEM Datasets to Model the Influence on ABF Images}, volume={24}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927618001575}, DOI={10.1017/S1431927618001575}, abstractNote={Thin film epitaxial strain plays an important role in controlling the behavior of materials, including electrical/magnetic properties and phase transitions. Further, epitaxial strain can mediate properties by inducing lattice distortions, such as octahedral rotations, at film/substrate interfaces [1]. Developing an understanding of these distortions is thus essential to control film properties for a given system. One method to characterization this distortion is position averaged convergent beam electron diffraction (PACBED), which is also used to precisely quantify sample thickness, orientation, tilt, and even polarization [2, 3]. With the introduction of 4D-STEM detectors, such as the EMPAD, PACBED patterns can be reconstructed after acquisition to map sample by averaging diffraction patterns over selected regions [4].}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Kumar, Abinash and Chang, Celesta S. and Grimley, Everett D. and Chen, Zhen and LeBeau, James M.}, year={2018}, month={Aug}, pages={216–217} }
 @article{cabral_zhang_dickey_lebeau_2018, title={Gradient chemical order in the relaxor Pb(Mg1∕3Nb2∕3)O3}, volume={112}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.5016561}, DOI={10.1063/1.5016561}, abstractNote={Here, we apply aberration-corrected scanning transmission electron microscopy to quantify chemical ordering in the relaxor Pb(Mg1∕3Nb2∕3)O3 (PMN). We find that contrary to the prevailing model of a binary distribution of chemically ordered regions within a disordered matrix, the degree of ordering smoothly varies within an ordered domain and approaches a minimum at anti-phase boundaries. These results provide direct insight into the nature of cation ordering in this important prototypical relaxor material.}, number={8}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Cabral, Matthew J. and Zhang, Shujun and Dickey, Elizabeth C. and LeBeau, James M.}, year={2018}, month={Feb}, pages={082901} }
 @article{eldred_harris_baker_irving_lebeau_2018, title={Imaging of Single Vacancies and Dopant Complexes in Aluminum Nitride}, volume={24}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927618000600}, DOI={10.1017/S1431927618000600}, abstractNote={To enable efficient aluminum nitride UV LEDs and power electronics, charge carrier concentration must be carefully engineered via dopant control. Silicon is the most studied and promising dopant in AlGaN systems, however it has been demonstrated that charge carrier concentration drops as Al content increases [1,2]. The prevailing explanation for the decrease in charge carrier concentration is that other defects compensate Si donors at high Si concentrations. The exact distribution and nature of the defects responsible have not been identified, however it is theorized that a complex with cation vacancies contribute to the effect [3]. The purpose of this study is to determine a method of identifying and mapping the vacancies and other defects in the material for the purpose of studying defect formation and confirming the statistical models used to guide growth techniques. In this presentation, we will discuss how high precision and accuracy scanning transmission electron microscopy (STEM) can be used to detect and map dopant complexes formed during metal-organic chemical vapor deposition crystal growth, specifically cation vacancies complexed with cation substitution dopants. We will present the approach to model the structure using DFT calculations in the Vienna ab initio Simulation Package (VASP 5.3.4). Specifically, formation energies determined using the grand canonical formalism are used to determine the relative concentrations of the different potential configurations of the Si Al -V Al complexes. Multislice simulations are then performed using the various calculated defect coordinates as a function of sample thicknesses and operating condition. To observe the effect of the defect, intensities and positions are then extracted from ADF STEM images as shown in Figure 1. ADF STEM with a detector inner semiangle of 28 mrad was used to maximize the signal from the weakly scattering aluminum and nitrogen. For a Si-vacancy complex, the relative intensity of the column decreases by an amount}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Eldred, Tim B. and Harris, Joshua S. and Baker, Jonathon N. and Irving, Douglas L. and LeBeau, James M.}, year={2018}, month={Aug}, pages={22–23} }
 @article{grimley_frisone_schenk_park_fancher_mikolajick_jones_schroeder_lebeau_2018, title={Insights into Texture and Phase Coexistence in Polycrystalline and Polyphasic Ferroelectric HfO2 Thin Films using 4D-STEM}, volume={24}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927618001411}, DOI={10.1017/S1431927618001411}, abstractNote={The realization of competitively scaled and reliable ferroelectric non-volatile memories has been hindered for several decades by absence of a ferroelectric that maintains sufficient polarization when integrated into a full CMOS flow scaled thicknesses of around 10 nm. In 2011, Böscke and coworkers [1] reported ferroelectricity in 10 nm thick HfO 2 thin films grown on Si (001) with atomic layer deposition (ALD), which has catalyzed research to realize next-generation memories with its ferroelectric properties. Epitaxial films have been grown, and the domain and grain sub-structuring of both epitaxial [2] and polycrystalline [3] HfO 2 have started to be revealed. Strain commonly imparts unique electrical and magnetic properties to many materials, and studies are revealing that HfO 2 is no exception. The growth of epitaxial non-centrosymmetric Pca2 1 orthorhombic HfO 2 shows an important dependence on the substrate [2], and first principles calculations have outlined the important stabilizing influence of grain size and surface energy for the various stable and metastable HfO 2 polymorphs [4,5]. ALD HfO 2 samples are crystallized between two polycrystalline TiN electrodes via rapid thermal annealing [1,3]. Thin films with small grain sizes with multiple HfO 2 polymorphs}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Grimley, Everett D. and Frisone, Sam and Schenk, Tony and Park, Min Hyuk and Fancher, Chris M. and Mikolajick, Thomas and Jones, Jacob L. and Schroeder, Uwe and LeBeau, James M.}, year={2018}, month={Aug}, pages={184–185} }
 @article{xu_dycus_lebeau_2018, title={Numerical modeling of specimen geometry for quantitative energy dispersive X-ray spectroscopy}, volume={184}, ISSN={["1879-2723"]}, DOI={10.1016/j.ultramic.2017.08.015}, abstractNote={Transmission electron microscopy specimens typically exhibit local distortion at thin foil edges, which can influence the absorption of X-rays for quantitative energy dispersive X-ray spectroscopy (EDS). Here, we report a numerical, three-dimensional approach to model the geometry of general specimens and its influence on quantification when using single and multiple detector configurations. As a function of specimen tilt, we show that the model correctly predicts the asymmetric nature of X-ray counts and ratios. When using a single detector, we show that complex specimen geometries can introduce significant uncertainty in EDS quantification. Further, we show that this uncertainty can be largely negated by collection with multiple detectors placed symmetrically about the sample such as the FEI Super-X configuration. Based on guidance provided by the model, we propose methods to reduce quantification error introduced by the sample shape. The source code is available at https://github.com/subangstrom/superAngle.}, journal={ULTRAMICROSCOPY}, author={Xu, W. and Dycus, J. H. and LeBeau, J. M.}, year={2018}, month={Jan}, pages={100–108} }
 @article{dhall_vigil-fowler_houston dycus_kirste_mita_sitar_collazo_lebeau_2018, title={Probing collective oscillation ofd-orbital electrons at the nanoscale}, volume={112}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.5012742}, DOI={10.1063/1.5012742}, abstractNote={Here, we demonstrate that high energy electrons can be used to explore the collective oscillation of s, p, and d orbital electrons at the nanometer length scale. Using epitaxial AlGaN/AlN quantum wells as a test system, we observe the emergence of additional features in the loss spectrum with the increasing Ga content. A comparison of the observed spectra with ab-initio theory reveals that the origin of these spectral features lies in excitations of 3d-electrons contributed by Ga. We find that these modes differ in energy from the valence electron plasmons in Al1–xGaxN due to the different polarizabilities of the d electrons. Finally, we study the dependence of observed spectral features on the Ga content, lending insights into the origin of these spectral features, and their coupling with electron-hole excitations.}, number={6}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Dhall, Rohan and Vigil-Fowler, Derek and Houston Dycus, J. and Kirste, Ronny and Mita, Seiji and Sitar, Zlatko and Collazo, Ramon and LeBeau, James M.}, year={2018}, month={Feb}, pages={061102} }
 @article{cabral_dickey_lebeau_2018, title={Quantification of Structural Correlation in STEM Images using the Projected Pair Distribution Function}, volume={24}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927618000788}, DOI={10.1017/S1431927618000788}, abstractNote={Picometer-scale structural distortion drives a wide range of material properties including pyroelectricity, ferroelectricity, and piezoelectricity. Further, since short-range correlations of chemistry and distortion in these systems manifest unique properties, it is crucial to quantify and understand how they contribute to material response. In this presentation, we will discuss application of the projected pair distribution function (pPDF) for identifying short-range structural correlation in STEM images. The pPDF, which is a 2D analogue of the PDF technique employed in diffraction, provides a representation of the distances between neighboring atom column pairs directly from STEM images as illustrated in Figure 1a [1]. The pPDF can be separated into partial pPDFs to investigate the distance distribution between constituent atom column types in an image [2]. As by the deviation,  of the peaks as a function}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Cabral, Matthew J. and Dickey, Elizabeth C. and LeBeau, James M.}, year={2018}, month={Aug}, pages={58–59} }
 @article{dycus_mirrielees_grimley_kirste_mita_sitar_collazo_irving_lebeau_2018, title={Structure of Ultrathin Native Oxides on III-Nitride Surfaces}, volume={10}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.8b00845}, abstractNote={When pristine material surfaces are exposed to air, highly reactive broken bonds can promote the formation of surface oxides with structures and properties differing greatly from bulk. Determination of the oxide structure is often elusive through the use of indirect diffraction methods or techniques that probe only the outermost layer. As a result, surface oxides forming on widely used materials, such as group III-nitrides, have not been unambiguously resolved, even though critical properties can depend sensitively on their presence. In this study, aberration corrected scanning transmission electron microscopy reveals directly, and with depth dependence, the structure of ultrathin native oxides that form on AlN and GaN surfaces. Through atomic resolution imaging and spectroscopy, we show that the oxide layers are comprised of tetrahedra-octahedra cation-oxygen units, in an arrangement similar to bulk θ-Al2O3 and β-Ga2O3. By applying density functional theory, we show that the observed structures are more stable than previously proposed surface oxide models. We place the impact of these observations in the context of key III-nitride growth, device issues, and the recent discovery of two-dimensional nitrides.}, number={13}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Dycus, J. Houston and Mirrielees, Kelsey J. and Grimley, Everett D. and Kirste, Ronny and Mita, Seiji and Sitar, Zlatko and Collazo, Ramon and Irving, Douglas L. and LeBeau, James M.}, year={2018}, month={Apr}, pages={10607–10611} }
 @article{chen_wang_wiaderek_sang_borkiewicz_chapman_lebeau_lynn_li_2018, title={Super Charge Separation and High Voltage Phase in NaxMnO2}, volume={28}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201805105}, abstractNote={Abstract}, number={50}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Chen, Xi and Wang, Yichao and Wiaderek, Kamila and Sang, Xiahan and Borkiewicz, Olaf and Chapman, Karena and LeBeau, James and Lynn, Jeffrey and Li, Xin}, year={2018}, month={Dec} }
 @article{xu_lebeau_2017, title={A Convolutional Neural Network Approach to Thickness Determination using Position Averaged Convergent Beam Electron Diffraction}, volume={23}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927617001283}, DOI={10.1017/S1431927617001283}, abstractNote={Position averaged convergent beam electron diffraction (PACBED) can accurately measure local specimen thickness with nanometer resolution, which is critical in quantitative scanning transmission electron microscopy (STEM) [1]. These thickness measurements are conducted by pattern matching experiment to simulations, either by least squares fitting (LSF) or by eye. This process, however, can be slow and inaccurate, since only slight contrast feature changes are used be distinguish patterns that are within a few nm. In recent years, convolutional neural networks (CNN) have shown excellent performance in tasks such as self-driving cars, face detection, and text recognition. With multiple convolutional layers in deep, CNN can automatically extract the local features from the images without any feature engineering procedures. The above advantage suggests the promising CNN application in determining thickness from PACBED with different image contrast and patterns. In this study, we seek a deep convolutional neural network approach to determine the local specimen thickness from PACBED with 1 nm resolution from 1 nm to 120 nm. Starting from a pre-trained AlexNet network[2], we transfer its network architecture to learn this new task[3]. Specifically, we keep the weights of convolutional and first two fully connected layers from the original AlexNet and replace the last fully-connected and softmax layer for 120 categories as illustrated in Figure 1. The weights in the network are fine-tuned in subsequent training by continuing the backpropagation with a 10 times faster learning rate in the last fully-connected layer. The total training process is conducted using about 5.8 million images, which are random affine transformed, brightness adjusted, rotated, and noise added from the simulated PACBED patterns in different thickness. To reduce the overfitting, dropout is applied in the fully connected layers with a ratio of 0.5[4]. The trained network shows 99.1% accuracy from the testing data (based on simulated PACBED patterns). The approach achieves an overall 85% accuracy when comparing experimentally acquired PACBED patterns, where}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Xu, Weizong and LeBeau, James M.}, year={2017}, month={Jul}, pages={120–121} }
 @article{park_schenk_fancher_grimley_zhou_richter_lebeau_jones_mikolajick_schroeder_2017, title={A comprehensive study on the structural evolution of HfO2 thin films doped with various dopants}, volume={5}, ISSN={["2050-7534"]}, DOI={10.1039/c7tc01200d}, abstractNote={Quantitative phase analysis is first performed on doped Hafnia films to elucidate the structural origin of unexpected ferroelectricity.}, number={19}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, author={Park, M. H. and Schenk, T. and Fancher, C. M. and Grimley, E. D. and Zhou, C. and Richter, C. and LeBeau, J. M. and Jones, J. L. and Mikolajick, T. and Schroeder, U.}, year={2017}, month={May}, pages={4677–4690} }
 @article{dycus_lebeau_2017, title={A reliable approach to prepare brittle semiconducting materials for cross-sectional transmission electron microscopy}, volume={268}, ISSN={["1365-2818"]}, DOI={10.1111/jmi.12601}, abstractNote={Summary}, number={3}, journal={JOURNAL OF MICROSCOPY}, author={Dycus, J. H. and Lebeau, J. M.}, year={2017}, month={Dec}, pages={225–229} }
 @article{findlay_chen_weyland_sang_xu_dycus_lebeau_allen_2017, title={Absolute-Scale Comparison with Simulation for Quantitative Energy-Dispersive X-Ray Spectroscopy in Atomic-Resolution Scanning Transmission Electron Microscopy}, volume={23}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927617002628}, DOI={10.1017/S1431927617002628}, abstractNote={In analytical electron microscopy}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Findlay, S.D. and Chen, Z. and Weyland, M. and Sang, X. and Xu, W. and Dycus, J.H. and LeBeau, J.M. and Allen, L.J.}, year={2017}, month={Jul}, pages={388–389} }
 @article{moghadam_xiao_ahmadi-majlan_grimley_bowden_ong_chambers_lebeau_hong_sushko_et al._2017, title={An Ultrathin Single Crystalline Relaxor Ferroelectric Integrated on a High Mobility Semiconductor}, volume={17}, ISSN={["1530-6992"]}, DOI={10.1021/acs.nanolett.7b02947}, abstractNote={The epitaxial growth of multifunctional oxides on semiconductors has opened a pathway to introduce new functionalities to semiconductor device technologies. In particular, the integration of gate materials that enable nonvolatile or hysteretic functionality in field-effect transistors could lead to device technologies that consume less power or allow for novel modalities in computing. Here we present electrical characterization of ultrathin single crystalline SrZrxTi1-xO3 (x = 0.7) films epitaxially grown on a high mobility semiconductor, Ge. Epitaxial films of SrZrxTi1-xO3 exhibit relaxor behavior, characterized by a hysteretic polarization that can modulate the surface potential of Ge. We find that gate layers as thin as 5 nm corresponding to an equivalent-oxide thickness of just 1.0 nm exhibit a ∼2 V hysteretic window in the capacitance-voltage characteristics. The development of hysteretic metal-oxide-semiconductor capacitors with nanoscale gate thicknesses opens new vistas for nanoelectronic devices.}, number={10}, journal={NANO LETTERS}, author={Moghadam, Reza M. and Xiao, Zhiyong and Ahmadi-Majlan, Kamyar and Grimley, Everett D. and Bowden, Mark and Ong, Phuong-Vu and Chambers, Scott A. and Lebeau, James M. and Hong, Xia and Sushko, Peter V. and et al.}, year={2017}, month={Oct}, pages={6248–6257} }
 @article{fitch_trappen_huang_zhou_cabrera_dong_kumari_holcomb_lebeau_2017, title={Combined EELS and XAS Analysis of the Relationship between Depth Dependence and Valence in LSMO Thin Films}, volume={23}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927617008662}, DOI={10.1017/S1431927617008662}, abstractNote={Lanthanum Strontium Manganite (LSMO) thin films are of interest due to their colossal magnetoresistive properties}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Fitch, Jim and Trappen, Robbyn and Huang, Chih-Yeh and Zhou, Jinling and Cabrera, Guerau and Dong, Shuai and Kumari, Shalini and Holcomb, Mikel B. and LeBeau, James M.}, year={2017}, month={Jul}, pages={1600–1601} }
 @article{grimley_wang_jalan_lebeau_2017, title={Compositional Ordering and Polar Nano-Regions: Physical Effects of Sn Alloying in SrTiO3 Thin Films}, volume={23}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927617008571}, DOI={10.1017/S1431927617008571}, abstractNote={. The properties accessible to perovskite oxides can be substantially modified through solid-solution alloying, which can even produce altogether new functionality. Recent theoretical studies, for example, have suggested that the excellent ferroelectric properties in Pb 2+ lead-based ferroelectrics might be alternatively obtained by stabilizing Sn as Sn 2+ in a perovskite [1]. Towards this end, heavily alloyed Sn:SrTiO 3 thin films were recently synthesized, and exhibited signatures of relaxor ferroelectricity in second harmonic generation experiments [2]. Relaxor-like ferroelectricity is usually thought to result from the formation of the polar nano-regions coupled to other changes in the crystal lattice, which are readily measureable with high-angle annular dark-field scanning transmission electron microscopy (HAADF STEM) [3]. In this talk, we explore the local changes in composition, strain, and non-centrosymmetric displacements in Sn alloyed SrTiO 3 thin films with accurate and precise STEM imaging. We will demonstrate inhomogeneity in the films consistent with compositional ordering and formation of polar nano-regions. Revolving}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Grimley, Everett D. and Wang, Tianqi and Jalan, Bharat and LeBeau, James M.}, year={2017}, month={Jul}, pages={1582–1583} }
 @article{cabral_zhang_chi_reich_dickey_lebeau_2017, title={Correlating Local Chemistry and Local Cation Displacements in the Relaxor Ferroelectric PMN}, volume={23}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927617008741}, DOI={10.1017/S1431927617008741}, abstractNote={Relaxor ferroelectrics are a unique class of materials that can be identified by their high dielectric constants, low hysteresis, large electrostrictive strains}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Cabral, Matthew J. and Zhang, Shujun and Chi, Jocelyn and Reich, Brian J. and Dickey, Elizabeth C. and LeBeau, James M.}, year={2017}, month={Jul}, pages={1616–1617} }
 @article{dhall_dycus_fowler_lebeau_2017, title={Emergence of the Collective Oscillations in Electron Energy Loss Spectra of d-electrons in III-V Nitrides}, volume={23}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927617002562}, DOI={10.1017/S1431927617002562}, abstractNote={In this work, we study the electron energy loss spectra of Aluminum-Gallium Nitride (AlGaN) materials. In particular, we focus on the low loss region of the EEL spectra, which show deviations from the classical Drude picture due to solid state effects. A comparison with ab-initio calculations yields insight into the origin of specific features in the observed spectra, and the role of electron-plasmon interaction.}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Dhall, Rohan and Dycus, Houston and Fowler, Derek Vigil and LeBeau, James M.}, year={2017}, month={Jul}, pages={376–377} }
 @article{jung_faucher_mukherjee_akey_ironside_cabral_sang_lebeau_bank_buonassisi_et al._2017, title={Highly tensile-strained Ge/InAlAs nanocomposites}, volume={8}, ISSN={2041-1723}, url={http://dx.doi.org/10.1038/NCOMMS14204}, DOI={10.1038/NCOMMS14204}, abstractNote={Abstract}, number={1}, journal={Nature Communications}, publisher={Springer Science and Business Media LLC}, author={Jung, Daehwan and Faucher, Joseph and Mukherjee, Samik and Akey, Austin and Ironside, Daniel J. and Cabral, Matthew and Sang, Xiahan and Lebeau, James and Bank, Seth R. and Buonassisi, Tonio and et al.}, year={2017}, month={Jan} }
 @article{dhall_dycus_cabral_grimley_xu_damiano_lebeau_2017, title={Novel FIB-less Fabrication of Electrical Devices for in-situ Biasing}, volume={23}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927617008170}, DOI={10.1017/S1431927617008170}, abstractNote={In this study, we report a novel fabrication scheme for in-situ electrical biasing of bulk material systems. This scheme integrates simple microelectronics fabrication processes with conventional TEM sample preparation through mechanical polishing, to produce electrical devices suitable for high resolution TEM/STEM studies under applied electrical bias. This is particularly crucial for applications such as quantitative STEM imaging, where FIB-induced sample damage distorts the image contrast, and prevents precise quantification.}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Dhall, Rohan and Dycus, Houston and Cabral, Matthew and Grimley, Everett and Xu, Weizong and Damiano, John and LeBeau, James M.}, year={2017}, month={Jul}, pages={1502–1503} }
 @article{xu_dycus_lebeau_2017, title={Numerical Modeling of Specimen Geometry for Quantitative Multiple Detector EDS}, volume={23}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S143192761700263X}, DOI={10.1017/S143192761700263X}, abstractNote={By combining multiple X-ray detectors to enlarge the total detector area, new energy dispersive X-ray spectrometers exhibit dramatically enhanced collection efficiency. This provides significantly higher signal-to-noise ratio, enabling elemental mapping at the atomic scale [1-4]. The increased complexity in multi-detector systems has also brought new challenges in terms of absorption correction and X-rays being shadowed by holder as a function of tilt. To this end, we have previously developed a numerical that combines detector geometry, holder shadowing, Be filtering, and specimen absorption to quantitatively analyze elemental quantification on an atom-column by atom-column basis [3,5]. The numerical model incorporates detector and holder geometries by angularly discretizing the collected X-rays [5]. The effective detector solid angle, Ω eff is determined by integrating over all discretized X-rays, i , collected from every sample slice along the depth direction, t , and then can be further used to quantify absolute counts and counts ratio of the sample.}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Xu, Weizong and Dycus, J. Houston and LeBeau, James M.}, year={2017}, month={Jul}, pages={390–391} }
 @article{lebeau_cabral_dycus_grimley_zhang_dickey_2017, title={Quantifying Local Structure of Complex Oxides Using Accurate and Precise Scanning Transmission Electron Microscopy}, volume={23}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927617008856}, DOI={10.1017/S1431927617008856}, abstractNote={Quantifying local structure is critical to understand and control material properties. While pair distribution function techniques from diffraction are commonly used to investigate the average local structure of a material, these approaches are limited by the lack of chemically and spatially resolved details. While electron microscopy exhibits superior spatial resolution, accurate determination of structure has been limited by imprecise knowledge of the illuminating and diffraction conditions (parallel beam) or sample drift (STEM). In contrast, the revolving STEM (RevSTEM) method introduces scan rotation between a series of fast-acquisition STEM images to encode the information about sample drift and leads to near distortion-free imaging after post-processing [1]}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={LeBeau, James M. and Cabral, Matthew and Dycus, J. Houston and Grimley, Everett and Zhang, Shujun and Dickey, Elizabeth}, year={2017}, month={Jul}, pages={1638–1639} }
 @article{richter_schenk_park_tscharntke_grimley_lebeau_zhou_fancher_jones_mikolajick_et al._2017, title={Si Doped Hafnium Oxide-A “Fragile” Ferroelectric System}, volume={3}, ISSN={2199-160X}, url={http://dx.doi.org/10.1002/AELM.201700131}, DOI={10.1002/AELM.201700131}, abstractNote={Abstract}, number={10}, journal={Advanced Electronic Materials}, publisher={Wiley}, author={Richter, Claudia and Schenk, Tony and Park, Min Hyuk and Tscharntke, Franziska A. and Grimley, Everett D. and LeBeau, James M. and Zhou, Chuanzhen and Fancher, Chris M. and Jones, Jacob L. and Mikolajick, Thomas and et al.}, year={2017}, month={Aug}, pages={1700131} }
 @article{dycus_xu_lebeau_2017, title={Standardless EDS Composition Analysis using Quantitative Annular Dark-Field Imaging}, volume={23}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927617003245}, DOI={10.1017/S1431927617003245}, abstractNote={Breakthroughs in energy dispersive X-ray detectors have greatly improved the signal-to-noise ratio of spatial mapping, leading to new interest for quantitative atomic scale elemental analysis. The most common method for EDS composition analysis in TEM is the Cliff-Lorimer ratio where the composition is directly related to the X-ray peak intensities and the Cliff-Lorimer factor, K, through: !" !# = k"# ∗ '( '# [1]. Although the method makes for a simple way to extract quantitative information, accurately calibrating K factors can be difficult. Another method for compositional EDS analysis is using the ζfactor approach where the characteristic X-ray intensities are related to the mass-thickness and composition [2]. For both quantitative methods, samples are tilted to minimize channeling conditions; however, orientation along a low-order zone axis, resulting in strong channeling, is required for atomic scale analysis. The necessity for on-zone acquisition has resulted in studies to account for channeling conditions to improve the quantitative capabilities of atomic scale EDS mapping [3]. An alternative method for determining composition is quantitative STEM (QSTEM) using the annular dark-field intensity [4-5]. In this approach, intensity is placed on an absolute scale and multislice image simulations are performed at varying composition and thickness values. Importantly, a standard with known composition is not needed for composition analysis using QSTEM and images are typically acquired at strong channeling conditions.}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Dycus, J. Houston and Xu, Weizong and LeBeau, James M.}, year={2017}, month={Jul}, pages={512–513} }
 @article{lim_ahmadi-majlan_grimley_du_bowden_moghadam_lebeau_chambers_ngai_2017, title={Structural and electrical properties of single crystalline SrZrO3 epitaxially grown on Ge (001)}, volume={122}, ISSN={["1089-7550"]}, DOI={10.1063/1.5000142}, abstractNote={We present structural and electrical characterization of SrZrO3 that has been epitaxially grown on Ge(001) by oxide molecular beam epitaxy. Single crystalline SrZrO3 can be nucleated on Ge via deposition at low temperatures followed by annealing at 550 °C in ultra-high vacuum. Photoemission spectroscopy measurements reveal that SrZrO3 exhibits a type-I band arrangement with respect to Ge, with conduction and valence band offsets of 1.4 eV and 3.66 eV, respectively. Capacitance-voltage and current-voltage measurements on 4 nm thick films reveal low leakage current densities and an unpinned Fermi level at the interface that allows modulation of the surface potential of Ge. Ultra-thin films of epitaxial SrZrO3 can thus be explored as a potential gate dielectric for Ge.}, number={8}, journal={JOURNAL OF APPLIED PHYSICS}, author={Lim, Z. H. and Ahmadi-Majlan, K. and Grimley, E. D. and Du, Y. and Bowden, M. and Moghadam, R. and LeBeau, J. M. and Chambers, S. A. and Ngai, J. H.}, year={2017}, month={Aug} }
 @article{dycus_mirrielees_grimley_dhall_kirste_mita_sitar_collazo_irving_lebeau_2017, title={Structure and Chemistry of Oxide Surface Reconstructions in III-Nitrides Observed using STEM EELS}, volume={23}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927617007887}, DOI={10.1017/S1431927617007887}, abstractNote={.}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Dycus, J. Houston and Mirrielees, Kelsey J. and Grimley, Everett D. and Dhall, Rohan and Kirste, Ronny and Mita, Seiji and Sitar, Zlatko and Collazo, Ramon and Irving, Douglas L. and LeBeau, James M.}, year={2017}, month={Jul}, pages={1444–1445} }
 @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{mitchell_lo_genc_lebeau_augustyn_2017, title={Transition from Battery to Pseudocapacitor Behavior via Structural Water in Tungsten Oxide}, volume={29}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.6b05485}, abstractNote={The kinetics of energy storage in transition metal oxides are usually limited by solid-state diffusion, and the strategy most often utilized to improve their rate capability is to reduce ion diffusion distances by utilizing nanostructured materials. Here, another strategy for improving the kinetics of layered transition metal oxides by the presence of structural water is proposed. To investigate this strategy, the electrochemical energy storage behavior of a model hydrated layered oxide, WO3·2H2O, is compared with that of anhydrous WO3 in an acidic electrolyte. It is found that the presence of structural water leads to a transition from battery-like behavior in the anhydrous WO3 to ideally pseudocapacitive behavior in WO3·2H2O. As a result, WO3·2H2O exhibits significantly improved capacity retention and energy efficiency for proton storage over WO3 at sweep rates as fast as 200 mV s–1, corresponding to charge/discharge times of just a few seconds. Importantly, the energy storage of WO3·2H2O at such rates ...}, number={9}, journal={CHEMISTRY OF MATERIALS}, author={Mitchell, James B. and Lo, William C. and Genc, Arda and LeBeau, James and Augustyn, Veronica}, year={2017}, month={May}, pages={3928–3937} }
 @article{xu_bowes_grimley_irving_lebeau_2017, title={Utilizing High-temperature Atomic-resolution STEM and EELS to Determine Reconstructed Surface Structure of Complex Oxide}, volume={23}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927617008649}, DOI={10.1017/S1431927617008649}, abstractNote={Surface reconstructions are conventionally characterized by scanning tunneling microscopy (STM), electron diffraction, or X-ray photoelectron spectroscopy (XPS) [1]. These methods indirectly determine the surface structure and chemistry, which requires subsequent structural refinement and confirmation by density functional theory (DFT). Complex oxide surface reconstructions not only involve atomic structural rearrangement, but also changes in surface stoichiometry or charge state. As the underlying crystal structure becomes more complicated, the surface tends to restructure into a variety of structures, affected by numerous factors such as surface polarization, temperature, and partial pressure. In the case when the surface structure changes with temperature, above indirect methods become limited [2]. A direct real-space characterization using scanning transmission electron microscopy (STEM) is thus ideal. However, it is still challenging to reveal surface atomic structure at high temperatures, particularly when additional surface chemical structure characterization is needed while maintaining the atomic-resolution.}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Xu, Weizong and Bowes, Preston C. and Grimley, Everett D. and Irving, Douglas L. and LeBeau, James M.}, year={2017}, month={Jul}, pages={1596–1597} }
 @article{xu_dycus_sang_lebeau_2016, title={A numerical model for multiple detector energy dispersive X-ray spectroscopy in the transmission electron microscope}, volume={164}, ISSN={["1879-2723"]}, DOI={10.1016/j.ultramic.2016.02.004}, abstractNote={Here we report a numerical approach to model a four quadrant energy dispersive X-ray spectrometer in the transmission electron microscope. The model includes detector geometries, specimen position and absorption, shadowing by the holder, and filtering by the Be carrier. We show that this comprehensive model accurately predicts absolute counts and intensity ratios as a function of specimen tilt and position. We directly compare the model to experimental results acquired with a FEI Super-X EDS four quadrant detector. The contribution from each detector to the sum is investigated. The program and source code can be downloaded from https://github.com/subangstrom/superAngle.}, journal={ULTRAMICROSCOPY}, author={Xu, W. and Dycus, J. H. and Sang, X. and LeBeau, J. M.}, year={2016}, month={May}, pages={51–61} }
 @article{oni_broderick_rajan_lebeau_2016, title={Atom site preference and gamma '/gamma mismatch strain in Ni-Al-Co-Ti superalloys}, volume={73}, ISSN={["1879-0216"]}, DOI={10.1016/j.intermet.2016.03.006}, abstractNote={The structure and chemistry of NiCoAlTi quaternary superalloys are investigated at the microstructural and atomic scale. Atom probe tomograghy (APT) is used to quantify phase compositions and elemental partitioning behavior. Using aberration corrected electron microscopy, the site occupancy of the atoms within the A3 B structure (L12–type) γ′ phase is determined via atomic resolution energy dispersive X-ray spectroscopy (EDX). Ni is observed to preferentially occupy the A sub-lattice positions for all alloys, while Al and Ti occupy the B sub-lattice. In contrast, Co's site preference changes from a random distribution to the A sub-lattice as the alloy composition changes, in agreement with theoretical predictions from literature. Finally, the lattice strain across the γ′/γ interfaces is measured as a function of alloy composition.}, journal={INTERMETALLICS}, author={Oni, A. A. and Broderick, S. R. and Rajan, K. and LeBeau, J. M.}, year={2016}, month={Jun}, pages={72–78} }
 @article{sang_lebeau_2016, title={Characterizing the response of a scintillator-based detector to single electrons}, volume={161}, ISSN={["1879-2723"]}, DOI={10.1016/j.ultramic.2015.11.008}, abstractNote={Here we report the response of a high angle annular dark field scintillator-based detector to single electrons. We demonstrate that care must be taken when determining the single electron intensity as significant discrepancies can occur when quantifying STEM images with different methods. To account for the detector response, we first image the detector using very low beam currents (∼8fA), and subsequently model the interval between consecutive single electrons events. We find that single electrons striking the detector present a wide distribution of intensities, which we show is not described by a simple function. Further, we present a method to accurately account for the electrons within the incident probe when conducting quantitative imaging. The role detector settings play on determining the single electron intensity is also explored. Finally, we extend our analysis to describe the response of the detector to multiple electron events within the dwell interval of each pixel.}, journal={ULTRAMICROSCOPY}, author={Sang, Xiahan and LeBeau, James M.}, year={2016}, month={Feb}, pages={3–9} }
 @article{nozariasbmarz_roy_zamanipour_dycus_cabral_lebeau_krasinski_vashaee_2016, title={Comparison of thermoelectric properties of nanostructured Mg2Si, FeSi2, SiGe, and nanocomposites of SiGe-Mg2Si, SiGe-FeSi2}, volume={4}, ISSN={["2166-532X"]}, DOI={10.1063/1.4966138}, abstractNote={Thermoelectric properties of nanostructured FeSi2, Mg2Si, and SiGe are compared with their nanocomposites of SiGe–Mg2Si and SiGe–FeSi2. It was found that the addition of silicide nanoinclusions to SiGe alloy maintained or increased the power factor while further reduced the thermal conductivity compared to the nanostructured single-phase SiGe alloy. This resulted in ZT enhancement of Si0.88Ge0.12–FeSi2 by ∼30% over the broad temperature range of 500-950 °C compared to the conventional Si0.80Ge0.20 alloy. The Si0.88Ge0.12–Mg2Si nanocomposite showed constantly increasing ZT versus temperature up to 950 °C (highest measured temperature) reaching ZT ∼ 1.3. These results confirm the concept of silicide nanoparticle-in-SiGe-alloy proposed earlier by Mingo et al. [Nano Lett. 9, 711–715 (2009)].}, number={10}, journal={APL MATERIALS}, author={Nozariasbmarz, Amin and Roy, Palash and Zamanipour, Zahra and Dycus, J. Houston and Cabral, Matthew J. and LeBeau, James M. and Krasinski, Jerzy S. and Vashaee, Daryoosh}, year={2016}, month={Oct} }
 @article{spurgeon_du_droubay_devaraj_sang_longo_yan_kotula_shutthanandan_bowden_et al._2016, title={Competing Pathways for Nucleation of the Double Perovskite Structure in the Epitaxial Synthesis of La2MnNiO6}, volume={28}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.6b00829}, abstractNote={Double perovskites of the form R2BB′O6 (where R is a rare earth cation and B and B′ are chemically distinct transition metal cations with half-filled and empty eg orbitals, respectively) are of significant interest for their magnetoelectric properties. La2MnNiO6 is particularly attractive because of its large expected ferromagnetic moment per formula unit (5 μB f.u.–1) and its semiconducting character. If the ideal structure nucleates, superexchange coupling can take place via the B—O—B′ bonds that form, and the moment per formula unit can attain its maximum theoretical value. However, we show that even in the case of layer-by-layer deposition via molecular beam epitaxy, the system can follow multiple reaction pathways that lead to deviations from the double perovskite structure. In particular, we observe a spatially extended phase in which B-site cation disorder occurs, resulting in Mn—O—Mn and Ni—O—Ni antiferromagnetic domains, as well as the formation of quasi-epitaxial, antiferromagnetic NiO nanoscale...}, number={11}, journal={CHEMISTRY OF MATERIALS}, author={Spurgeon, Steven R. and Du, Yingge and Droubay, Timothy and Devaraj, Arun and Sang, Xiahan and Longo, Paolo and Yan, Pengfei and Kotula, Paul G. and Shutthanandan, Vaithiyalingam and Bowden, Mark E. and et al.}, year={2016}, month={Jun}, pages={3814–3822} }
 @article{eiteneer_pálsson_nemšák_gray_kaiser_son_lebeau_conti_greer_keqi_et al._2016, title={Depth-Resolved Composition and Electronic Structure of Buried Layers and Interfaces in a LaNiO3/SrTiO3 Superlattice from Soft- and Hard- X-ray Standing-Wave Angle-Resolved Photoemission}, volume={211}, ISSN={0368-2048}, url={http://dx.doi.org/10.1016/J.ELSPEC.2016.04.008}, DOI={10.1016/J.ELSPEC.2016.04.008}, abstractNote={LaNiO3 (LNO) is an intriguing member of the rare-earth nickelates in exhibiting a metal-insulator transition for a critical film thickness of about 4 unit cells [Son et al., Appl. Phys. Lett. 96, 062114 (2010)]; however, such thin films also show a transition to a metallic state in superlattices with SrTiO3 (STO) [Son et al., Appl. Phys. Lett. 97, 202109 (2010)]. In order to better understand this transition, we have studied a strained LNO/STO superlattice with 10 repeats of [4 unit-cell LNO/3 unit-cell STO] grown on an (LaAlO3)0.3(Sr2AlTaO6)0.7 substrate using soft x-ray standing-wave-excited angle-resolved photoemission (SWARPES), together with soft- and hard- x-ray photoemission measurements of core levels and densities-of-states valence spectra. The experimental results are compared with state-of-the-art density functional theory (DFT) calculations of band structures and densities of states. Using core-level rocking curves and x-ray optical modeling to assess the position of the standing wave, SWARPES measurements are carried out for various incidence angles and used to determine interface-specific changes in momentum-resolved electronic structure. We further show that the momentum-resolved behavior of the Ni 3d eg and t2g states near the Fermi level, as well as those at the bottom of the valence bands, is very similar to recently published SWARPES results for a related La0.7Sr0.3MnO3/SrTiO3 superlattice that was studied using the same technique (Gray et al., Europhysics Letters 104, 17004 (2013)), which further validates this experimental approach and our conclusions. Our conclusions are also supported in several ways by comparison to DFT calculations for the parent materials and the superlattice, including layer-resolved density-of-states results.}, journal={Journal of Electron Spectroscopy and Related Phenomena}, publisher={Elsevier BV}, author={Eiteneer, D. and Pálsson, G.K. and Nemšák, S. and Gray, A.X. and Kaiser, A.M. and Son, J. and LeBeau, J. and Conti, G. and Greer, A.A. and Keqi, A. and et al.}, year={2016}, month={Aug}, pages={70–81} }
 @article{eiteneer_palsson_nemsak_gray_kaiser_son_lebeau_conti_greer_kaqi_et al._2016, title={Depth-resolved composition and electronic structure of buried layers and interfaces in a LaNiO3/SrTiO3 superlatticefroni soft- and hard-X-ray standing-wave angle-resolved photoemission}, volume={211}, journal={Journal of Electron Spectroscopy and Related Phenomena}, author={Eiteneer, D. and Palsson, G. K. and Nemsak, S. and Gray, A. X. and Kaiser, A. M. and Son, J. and LeBeau, J. and Conti, G. and Greer, A. A. and Kaqi, A. and et al.}, year={2016}, pages={70–81} }
 @article{cabral_zhang_dickey_lebeau_2016, title={Direct observation of local chemistry and local cation displacements in the relaxor ferroelectric PMN-PT}, volume={22}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927616007856}, DOI={10.1017/S1431927616007856}, abstractNote={Picometer-scale lattice distortions play an important role on the macroscopic properties of relaxor ferroelectric materials. Due to competition between composition/charge ordering in these materials, there is a formation of “polar nanoregions” where local fluctuations in the B-site give rise to inhomogeneities in local strain and polarization on the nanometer scale. Direct real-space visualization of these distortions and local chemical composition can provide important insight into the formation of these “polar nanoregions”.}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Cabral, Matthew J. and Zhang, Shujun and Dickey, Elizabeth C. and LeBeau, James M.}, year={2016}, month={Jul}, pages={1402–1403} }
 @inproceedings{schroeder_pesic_schenk_mulaosmanovic_slesazeck_ocker_richter_yurchuk_khullar_muller_et al._2016, title={Impact of field cycling on HfO2 based non-volatile memory devices}, booktitle={2016 46th european solid-state device research conference (essderc)}, author={Schroeder, U. and Pesic, M. and Schenk, T. and Mulaosmanovic, H. and Slesazeck, S. and Ocker, J. and Richter, C. and Yurchuk, E. and Khullar, K. and Muller, J. and et al.}, year={2016}, pages={364–368} }
 @article{xu_bowes_grimley_irving_lebeau_2016, title={In-situ real-space imaging of single crystal surface reconstructions via electron microscopy}, volume={109}, ISSN={["1077-3118"]}, url={http://dx.doi.org/10.1063/1.4967978}, DOI={10.1063/1.4967978}, abstractNote={Here, we report a high temperature in-situ atomic resolution scanning transmission electron microscopy (STEM) study of single crystal surface structure dynamics. With the approach, we gain direct insight into a double layer reconstruction that occurs on the polar SrTiO3 (110) surface. We find that structural details of this reconstruction can be directly attributed to charge redistribution and the thermal mismatch between the surface and the bulk material. Periodic surface defects, similar to dislocations, are found, which act to relieve stress as the temperature is lowered. Combining STEM observations, electron energy loss spectroscopy, and density functional theory, we highlight the combined role of lattice misfit and charge compensation to determine the structure and chemistry of the observed polar surface reconstruction.}, number={20}, journal={APPLIED PHYSICS LETTERS}, author={Xu, Weizong and Bowes, Preston C. and Grimley, Everett D. and Irving, Douglas L. and LeBeau, James M.}, year={2016}, month={Nov} }
 @article{xu_grimley_lebeau_2016, title={In-situ-by-Ex-situ:
               
               FIB-less Preparation of Bulk Samples on Heating Membranes for Atomic Resolution STEM Imaging}, volume={22}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927616004724}, DOI={10.1017/S1431927616004724}, abstractNote={Recent advances in in-situ electron microscopy have enabled materials characterization to a new level. Namely, advanced in-situ electron microscopy sample holders integrated with heating, liquid, or gas environmental cells have permitted the investigation of kinetic processes while maintaining atomic resolution [1]. Even with these impressive advancements, however, much in-situ work has been performed on nanoparticles and their supporters by dispersing liquid drops onto grids. For these samples, it is often difficult to precisely align along a low order zone axis, which is required for atomic resolution STEM imaging. For bulk samples prepared by FIB, the Ga contamination and/or the protective layer can cause unwanted reactions that prevent observation of pristine surfaces and interfaces. As a result, few works have successfully shown atomic resolution STEM imaging at temperatures higher than 700 °C for membrane based devices [1, 2]. Given these complications, quantitative, or even qualitative, structural and chemical analysis of bulk samples at high temperature remains challenging.}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Xu, Weizong and Grimley, Everett D. and LeBeau, James M.}, year={2016}, month={Jul}, pages={774–775} }
 @article{dycus_xu_sang_d'alfonso_chen_weyland_allen_findlay_lebeau_2016, title={Influence of experimental conditions on atom column visibility in energy dispersive X-ray spectroscopy}, volume={171}, ISSN={0304-3991}, url={http://dx.doi.org/10.1016/J.ULTRAMIC.2016.08.013}, DOI={10.1016/J.ULTRAMIC.2016.08.013}, abstractNote={Here we report the influence of key experimental parameters on atomically resolved energy dispersive X-ray spectroscopy (EDX). In particular, we examine the role of the probe forming convergence semi-angle, sample thickness, lattice spacing, and dwell/collection time. We show that an optimum specimen-dependent probe forming convergence angle exists to maximize the signal-to-noise ratio of the atomically resolved signal in EDX mapping. Furthermore, we highlight that it can be important to select an appropriate dwell time to efficiently process the X-ray signal. These practical considerations provide insight for experimental parameters in atomic resolution energy dispersive X-ray analysis.}, journal={Ultramicroscopy}, publisher={Elsevier BV}, author={Dycus, J.H. and Xu, W. and Sang, X. and D'Alfonso, A.J. and Chen, Z. and Weyland, M. and Allen, L.J. and Findlay, S.D. and LeBeau, J.M.}, year={2016}, month={Dec}, pages={1–7} }
 @article{spurgeon_du_droubay_devaraj_sang_longo_yan_kotula_shutthanandan_bowden_et al._2016, title={Multidimensional Analysis of Nanoscale Phase Separation in Complex Materials Systems}, volume={22}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927616002269}, DOI={10.1017/S1431927616002269}, abstractNote={Propelled by rapid advances in synthesis, characterization, and computational modeling, materials science is fast progressing toward a “materials-by-design” paradigm. While this new approach offers the promise of “designer” materials, it has tended to overlook the complex kinetic limitations that hinder the realization of the targeted materials systems. In particular, while we can envision a very large number of materials combinations, we are unable to synthesize them in practice because existing characterization and modeling approaches fail to capture the inherent complexities of such systems. This shortcoming is amplified by the fundamental disconnect between highly local and volume-averaged structure-property models resulting from electron microscopy and X-ray diffraction investigations, respectively. Our study addresses the grand challenge of multicomponent materials design, using a multidimensional analysis approach to achieve a predictive understanding of structure-property relationships in a model system. Here we explore the model complex oxide, La 2 MnNiO 6 (LMNO), which possesses a hierarchy of structural, chemical, and magnetic ordering across multiple length scales. This material shows great promise for next-generation spintronics and thermoelectrics, but its implementation is hindered by a poor understanding of the underlying structure that governs its macroscale magnetic performance [1]. Using aberration-corrected scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (STEM-EDS)}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Spurgeon, Steven R. and Du, Yingge and Droubay, Timothy and Devaraj, Arun and Sang, Xiahan and Longo, Paolo and Yan, Pengfei and Kotula, Paul G. and Shutthanandan, Vaithiyalingam and Bowden, Mark E. and et al.}, year={2016}, month={Jul}, pages={282–283} }
 @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{pesic_fengler_larcher_padovani_schenk_grimley_sang_lebeau_slesazeck_schroeder_et al._2016, title={Physical Mechanisms behind the Field-Cycling Behavior of HfO2-Based Ferroelectric Capacitors}, volume={26}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201600590}, abstractNote={Novel hafnium oxide (HfO2)‐based ferroelectrics reveal full scalability and complementary metal oxide semiconductor integratability compared to perovskite‐based ferroelectrics that are currently used in nonvolatile ferroelectric random access memories (FeRAMs). Within the lifetime of the device, two main regimes of wake‐up and fatigue can be identified. Up to now, the mechanisms behind these two device stages have not been revealed. Thus, the main scope of this study is an identification of the root cause for the increase of the remnant polarization during the wake‐up phase and subsequent polarization degradation with further cycling. Combining the comprehensive ferroelectric switching current experiments, Preisach density analysis, and transmission electron microscopy (TEM) study with compact and Technology Computer Aided Design (TCAD) modeling, it has been found out that during the wake‐up of the device no new defects are generated but the existing defects redistribute within the device. Furthermore, vacancy diffusion has been identified as the main cause for the phase transformation and consequent increase of the remnant polarization. Utilizing trap density spectroscopy for examining defect evolution with cycling of the device together with modeling of the degradation results in an understanding of the main mechanisms behind the evolution of the ferroelectric response.}, number={25}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Pesic, Milan and Fengler, Franz Paul Gustav and Larcher, Luca and Padovani, Andrea and Schenk, Tony and Grimley, Everett D. and Sang, Xiahan and LeBeau, James M. and Slesazeck, Stefan and Schroeder, Uwe and et al.}, year={2016}, month={Jul}, pages={4601–4612} }
 @article{lebeau_sang_dycus_nui_irving_2016, title={Probing the subtleties of atomic distortions through accurate STEM imaging and density functional theory}, volume={22}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927616007844}, DOI={10.1017/S1431927616007844}, abstractNote={While aberration correction has unlocked previously inaccessible information at the atomic scale, real-space measurements of atomic displacements and distances have remained largely qualitative for scanning transmission electron microscopy (STEM). In particular, accuracy and precision in STEM is significantly hampered by the presence of sample drift and scan distortion. While sample drift is usually the dominate consideration, the scan system calibration is rarely perfectly orthonormal, which can introduce significant errors. These limitations have obscured the capabilities to directly characterize minute atomic structure changes that can ultimately control properties. In this talk, we will show how revolving scanning transmission electron microscopy (RevSTEM) is able to achieve highly accurate imaging on a routine basis [1]. The method uses a series of fast-acquisition STEM images, but with the scan coordinates rotated between successive frames. This, however, only accounts for the drift introduced distortion. Equipped with the Atom Column Indexing approach [2], we will introduce a method to very accurately and precisely correct the global scan coordinate system, to ensure a near-perfectly orthonormal scan. We will demonstrate the stability of this correction and that the combination of RevSTEM with such a corrected scan system is capable of achieving sub-picometer accuracy of real-space crystallographic measurements in STEM [3]. Multiple case studies will be presented to demonstrate the power of this new technique in combination with density functional theory. For example, we will show how picometer precise measurements enable the capability to directly observe static atomic displacements within a complex oxide and chalcogenide solid solutions [3, 4]. These subtle distortions will be examined using density functional theory to investigate the role of local chemical fluctuations and the influence of bond strengths. With the level of accuracy afforded by this imaging approach we will show how concepts used in analyzing total diffraction data, such as the pair distribution function (PDF), can be applied to STEM data. To do so, we will introduce the projected-PDF to analyze correlation between displacements spanning the entire image [4]. Furthermore, we will also show how RevSTEM images}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={LeBeau, James and Sang, Xiahan and Dycus, J. Houston and Nui, Changning and Irving, Douglas}, year={2016}, month={Jul}, pages={1400–1401} }
 @article{pham_dycus_lebeau_manga_muralidharan_corral_2016, title={Processing Low-Oxide ZrB2 Ceramics with High Strength Using Boron Carbide and Spark Plasma Sintering}, volume={99}, ISSN={["1551-2916"]}, DOI={10.1111/jace.14253}, abstractNote={A phase diagram‐assisted powder processing approach is shown to produce low‐oxygen (0.06 wt%O) ZrB2 ceramics using minimal B4C additions (0.25 wt%) and spark plasma sintering. Scanning electron microscopy and scanning transmission electron microscopy with elemental spectroscopy are used to identify “trash collector” oxides. These “trash collector” oxides are composed of manufacturer metal powder impurities that form discreet oxide particles due to the absence of standard Zr–B oxides found in high oxygen samples. A preliminary Zr–B–C–O quaternary thermodynamic database developed as a part of this work was used to calculate the ZrO2–B4C pseudobinary phase diagram and ZrB2–ZrO2–B4C pseudoternary phase diagrams. We use the calculated equilibrium phase diagrams to characterize the oxide impurities and show the direct reaction path that allows for the formation of ZrB2 with an oxygen content of 0.06 wt%, fine grains (3.3 μm) and superior mechanical properties (flexural strength of 660 MPa).}, number={8}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Pham, David and Dycus, Joseph Houston and LeBeau, James M. and Manga, Venkateswara R. and Muralidharan, Krishna and Corral, Erica L.}, year={2016}, month={Aug}, pages={2585–2592} }
 @article{chen_weyland_sang_xu_dycus_lebeau_d'alfonso_allen_findlay_2016, title={Quantitative atomic resolution elemental mapping via absolute-scale energy dispersive X-ray spectroscopy}, volume={168}, ISSN={["1879-2723"]}, DOI={10.1016/j.ultramic.2016.05.008}, abstractNote={Quantitative agreement on an absolute scale is demonstrated between experiment and simulation for two-dimensional, atomic-resolution elemental mapping via energy dispersive X-ray spectroscopy. This requires all experimental parameters to be carefully characterized. The agreement is good, but some discrepancies remain. The most likely contributing factors are identified and discussed. Previous predictions that increasing the probe forming aperture helps to suppress the channelling enhancement in the average signal are confirmed experimentally. It is emphasized that simple column-by-column analysis requires a choice of sample thickness that compromises between being thick enough to yield a good signal-to-noise ratio while being thin enough that the overwhelming majority of the EDX signal derives from the column on which the probe is placed, despite strong electron scattering effects.}, journal={ULTRAMICROSCOPY}, author={Chen, Z. and Weyland, M. and Sang, X. and Xu, W. and Dycus, J. H. and LeBeau, J. M. and D'Alfonso, A. J. and Allen, L. J. and Findlay, S. D.}, year={2016}, month={Sep}, pages={7–16} }
 @article{dycus_xu_lichtenwalner_hull_palmour_lebeau_2016, title={Resolving Atomic Scale Chemistry and Structure at NO and Ba Passivated SiC/SiO
               2 
               Interfaces}, volume={22}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927616009132}, DOI={10.1017/S1431927616009132}, abstractNote={Silicon carbide has become a commonly used wide-bandgap material for power devices. A major challenge for SiC MOSFET device processing has been to reduce the density of trap states at the SiC/SiO2 interface, which greatly reduces the inversion-layer field effect mobility, μFE, Nitric oxide (NO) annealing is commonly performed to passivate the SiC/SiO2 interface and reduce the interface trap density. A new method for increasing μFE involves depositing a layer of Ba at the interface which has been shown to produce μFE values up to 85 !"! !∗! [1], more than double that with the NO anneal. The impact of the SiC/SiO2 interface on μFE has driven research towards studying the transition layer between SiC and SiO2 [2]. Although studies report chemical segregation of N in NO annealed devices [3], the influence of Ba is unreported. Further, the influence of interfacial treatments on the atomic structure remains unclear even for NO annealed devices.}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Dycus, J. Houston and Xu, Weizong and Lichtenwalner, Daniel J. and Hull, Brett and Palmour, John W. and LeBeau, James M.}, year={2016}, month={Jul}, pages={1658–1659} }
 @article{grimley_schenk_sang_pesic_schroeder_mikolajick_lebeau_2016, title={Structural Changes Underlying Field-Cycling Phenomena in Ferroelectric HfO2 Thin Films}, volume={2}, ISSN={["2199-160X"]}, DOI={10.1002/aelm.201600173}, abstractNote={Since 2011, ferroelectric HfO2 has attracted growing interest in both fundamental and application oriented groups. In this material, noteworthy wake‐up and fatigue effects alter the shape of the polarization hysteresis loop during field cycling. Such changes are problematic for application of HfO2 to ferroelectric memories, which require stable polarization hystereses. Herein, electrical and structural techniques are implemented to unveil how cyclic switching changes nanoscale film structure, which modifies the polarization hysteresis. Impedance spectroscopy and scanning transmission electron microscopy identify regions with different dielectric and conductive properties in films at different cycling stages, enabling development of a structural model to explain the wake‐up and fatigue phenomena. The wake‐up regime arises due to changes in bulk and interfacial structuring: the bulk undergoes a phase transformation from monoclinic to orthorhombic grains, and the interfaces show changes in and diminishment of a nonuniform, defect rich, tetragonal HfO2 layer near the electrodes. The evolution of these aspects of structuring contributes to the increase in Pr and the opening of the constricted P–V hysteresis that are known to occur with wake‐up. The onset of the fatigue regime is correlated to an increasing concentration of bulk defects, which are proposed to pin domain walls.}, number={9}, journal={ADVANCED ELECTRONIC MATERIALS}, author={Grimley, Everett D. and Schenk, Tony and Sang, Xiahan and Pesic, Milan and Schroeder, Uwe and Mikolajick, Thomas and LeBeau, James M.}, year={2016}, month={Sep} }
 @article{dycus_xu_lichtenwalner_hull_palmour_lebeau_2016, title={Structure and chemistry of passivated SiC/SiO2 interfaces}, volume={108}, ISSN={["1077-3118"]}, DOI={10.1063/1.4951677}, abstractNote={Here, we report on the chemistry and structure of 4H-SiC/SiO2 interfaces passivated either by nitric oxide annealing or Ba deposition. Using aberration corrected scanning transmission electron microscopy and spectroscopy, we find that Ba and N remain localized at SiC/SiO2 interface after processing. Further, we find that the passivating species can introduce significant changes to the near-interface atomic structure of SiC. Specifically, we quantify significant strain for nitric oxide annealed sample where Si dangling bonds are capped by N. In contrast, strain is not observed at the interface of the Ba treated samples. Finally, we place these results in the context of field effect mobility.}, number={20}, journal={APPLIED PHYSICS LETTERS}, author={Dycus, J. Houston and Xu, Weizong and Lichtenwalner, Daniel J. and Hull, Brett and Palmour, John W. and LeBeau, James M.}, year={2016}, month={May} }
 @article{zaddach_niu_oni_fan_lebeau_irving_koch_2016, title={Structure and magnetic properties of a multi-principal element Ni-Fe-Cr-Co-Zn-Mn alloy}, volume={68}, ISSN={["1879-0216"]}, DOI={10.1016/j.intermet.2015.09.009}, abstractNote={A nanocrystalline alloy with a nominal composition of Ni20Fe20Cr20Co20Zn15Mn5 was produced by mechanical alloying and processed using annealing treatments between 450 and 600 °C for lengths from 0.5 to 4 h. Analysis was conducted using x-ray diffraction, transmission electron microscopy, magnetometry, and first-principles calculations. Despite designing the alloy using empirical high-entropy alloy guidelines, it was found to precipitate numerous phases after annealing. These precipitates included a magnetic phase, α-FeCo, which, after the optimal heat treatment conditions of 1 h at 500 °C, resulted in an alloy with reasonably good hard magnetic properties. The effect of annealing temperature and time on the microstructure and magnetic properties are discussed, as well as the likely mechanisms that cause the microstructure development.}, journal={INTERMETALLICS}, author={Zaddach, A. J. and Niu, C. and Oni, A. A. and Fan, M. and LeBeau, J. M. and Irving, D. L. and Koch, C. C.}, year={2016}, month={Jan}, pages={107–112} }
 @article{haislmaier_grimley_biegalski_lebeau_trolier-mckinstry_gopalan_engel-herbert_2016, title={Unleashing Strain Induced Ferroelectricity in Complex Oxide Thin Films via Precise Stoichiometry Control}, volume={26}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201602767}, abstractNote={Strain tuning has emerged as a powerful means to enhance properties and to induce otherwise unattainable phenomena in complex oxide films. However, by employing strain alone, the predicted properties sometimes fail to emerge. In this work, the critical role of precise stoichiometry control for realizing strain‐induced ferroelectricity in CaTiO3 films is demonstrated. An adsorption controlled growth window is discovered for CaTiO3 films grown by hybrid molecular beam epitaxy, which ensures an excellent control over the Ti:Ca atomic percent ratio of <0.8% in the films. Superior ferroelectric and dielectric properties are found for films grown inside the stoichiometric growth window, yielding maximum polarization, dielectric constant, and paraelectric‐to‐ferroelectric transition temperatures. Outside this growth window, properties are severely deteriorated and ultimately suppressed by defects in the films. This study exemplifies the important role of precise compositional control for achieving strain‐induced properties. Untangling the effects of strain and stoichiometry on functional properties will accelerate both fundamental discoveries yet to be made in the vast materials design space of strained complex oxide films, as well as utilization of strain‐stabilized phenomena in future devices.}, number={40}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Haislmaier, Ryan C. and Grimley, Everett D. and Biegalski, Michael D. and LeBeau, James M. and Trolier-McKinstry, Susan and Gopalan, Venkatraman and Engel-Herbert, Roman}, year={2016}, month={Oct}, pages={7271–7279} }
 @article{dycus_harris_sang_fancher_findlay_oni_chan_koch_jones_allen_et al._2015, title={Accurate Nanoscale Crystallography in Real-Space Using Scanning Transmission Electron Microscopy}, volume={21}, ISSN={["1435-8115"]}, DOI={10.1017/s1431927615013732}, abstractNote={Abstract}, number={4}, journal={MICROSCOPY AND MICROANALYSIS}, author={Dycus, J. Houston and Harris, Joshua S. and Sang, Xiahan and Fancher, Chris M. and Findlay, Scott D. and Oni, Adedapo A. and Chan, Tsung-ta E. and Koch, Carl C. and Jones, Jacob L. and Allen, Leslie J. and et al.}, year={2015}, month={Aug}, pages={946–952} }
 @article{jones_lebeau_nikkel_oni_dycus_cozzan_lin_chernatynskiy_nino_sinnott_et al._2015, title={Combined Experimental and Computational Methods Reveal the Evolution of Buried Interfaces during Synthesis of Ferroelectric Thin Films}, volume={2}, ISSN={2196-7350}, url={http://dx.doi.org/10.1002/ADMI.201500181}, DOI={10.1002/ADMI.201500181}, abstractNote={Understanding interfaces between dissimilar materials is crucial to the development of modern technologies, for example, semiconductor–dielectric and thermoelectric–semiconductor interfaces in emerging electronic devices. However, the structural characterization of buried interfaces is challenging because many measurement techniques are surface sensitive by design. When interested in interface evolution during synthesis, the experimental challenges multiply and often necessitate in situ techniques. For solution‐derived lead zirconate titanate (PZT) ferroelectric thin films, the evolution of buried interfaces during synthesis (including dielectric–metal and metal–metal) is thought to dramatically influence the resultant dielectric and ferroelectric properties. In the present work, multiple experimental and computational methods are combined to characterize interface evolution during synthesis of ferroelectric PZT films on platinized Si wafers—including in situ X‐ray diffraction during thermal treatment, aberration‐corrected scanning transmission electron microscopy of samples quenched from various synthesis states, and calculations using density functional theory. Substantial interactions at buried interfaces in the PZT/Pt/Ti/SiO
x
/Si heterostructure are observed and discussed relative to their role(s) in the synthesis process. The results prove that perovskite PZT nucleates directly from the platinum (111)‐oriented bottom electrode and reveal the roles of Pb and O diffusion and intermetallic Pt3Pb and Pt3Ti phases.}, number={10}, journal={Advanced Materials Interfaces}, publisher={Wiley}, author={Jones, Jacob L. and LeBeau, James M. and Nikkel, Jason and Oni, Adedapo A. and Dycus, J. Houston and Cozzan, Clayton and Lin, Fang-Yin and Chernatynskiy, Aleksandr and Nino, Juan C. and Sinnott, Susan B. and et al.}, year={2015}, month={Jun}, pages={1500181} }
 @article{oni_sang_kumar_sinnott_lebeau_2015, title={Direct Observation of Chemical Pressure in Intermetallic Alloys by Scanning Transmission Electron Microscopy}, volume={21}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927615008375}, DOI={10.1017/S1431927615008375}, abstractNote={As solute atoms are added to intermetallic compounds, local chemically induced pressure develops and results in atomic displacements. These distortions play a critical role in defining the mechanical behavior of these materials, for example, by impeding dislocation motion. While indirect methods, such as diffraction determined pair distribution functions, can access the average structure, spatially resolved information is lost. Scanning transmission electron microscopy (STEM), on the other hand, possess excellent spatial resolution, but image distortions often limit the ability to accurately and precisely measure projected crystal structure.}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Oni, Adedapo A. and Sang, Xiahan and Kumar, Aakash and Sinnott, Susan B. and LeBeau, James M.}, year={2015}, month={Aug}, pages={1519–1520} }
 @article{sang_grimley_niu_irving_lebeau_2015, title={Direct observation of charge mediated lattice distortions in complex oxide solid solutions}, volume={106}, ISSN={["1077-3118"]}, DOI={10.1063/1.4908124}, abstractNote={Using aberration corrected scanning transmission electron microscopy combined with advanced imaging methods, we directly observe atom column specific, picometer-scale displacements induced by local chemistry in a complex oxide solid solution. Displacements predicted from density functional theory were found to correlate with the observed experimental trends. Further analysis of bonding and charge distribution was used to clarify the mechanisms responsible for the detected structural behavior. By extending the experimental electron microscopy measurements to previously inaccessible length scales, we identified correlated atomic displacements linked to bond differences within the complex oxide structure.}, number={6}, journal={APPLIED PHYSICS LETTERS}, author={Sang, Xiahan and Grimley, Everett D. and Niu, Changning and Irving, Douglas L. and LeBeau, James M.}, year={2015}, month={Feb} }
 @article{raju_oni_godwal_yan_drozd_srinivasan_lebeau_rajan_saxena_2015, title={Effect of B and Cr on elastic strength and crystal structure of Ni3Al alloys under high pressure}, volume={619}, ISSN={["1873-4669"]}, DOI={10.1016/j.jallcom.2014.09.012}, abstractNote={Samples of Ni3Al, Ni3Al:B and Ni–Al–Cr super alloys were prepared by directional solidification method and their effect of alloying with ternary elements on the mechanical properties was investigated. In-situ X-ray diffraction studies were carried out on undoped Ni3Al, Ni3Al:B with boron 500 ppm and Ni–Al–Cr with 7.5 at.% of chromium super alloys at high pressure using diamond anvil cell. The results indicate that micro-alloying with B forms γ′-phase (L12 structure), similar to the pure Ni 3Al, while Ni–Al–Cr alloy consists of γ′ precipitates in a matrix of γ-phase (Ni-FCC structure). The crystal structure of all three alloys was stable up to 20 GPa. Micro alloying with boron increases bulk modulus of Ni3Al by 8% whereas alloying with chromium has the opposite effect decreasing the modulus by 11% when compared to undoped alloy. Further, the elastic modulus and hardness of Ni3Al, Ni3Al:B and Ni–Al–Cr alloys were determined using the nano-indentation technique, in combination with compressibility data which enabled the estimation of shear modulus and Poisson’s ratio of these alloys.}, journal={JOURNAL OF ALLOYS AND COMPOUNDS}, author={Raju, S. V. and Oni, A. A. and Godwal, B. K. and Yan, J. and Drozd, V. and Srinivasan, S. and LeBeau, J. M. and Rajan, K. and Saxena, S. K.}, year={2015}, month={Jan}, pages={616–620} }
 @article{xu_dycus_sang_oni_lebeau_2015, title={Effect of Specimen Geometry on Quantitative EDS Analysis with Four-Quadrant Super-X Detectors}, volume={21}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927615006248}, DOI={10.1017/S1431927615006248}, abstractNote={In recent years, X-ray signal collection efficiency in energy dispersive X-ray spectrometry (EDS) has been significantly improved by incorporating state-of-the-art four-quadrant Super-X detectors in aberration-corrected microscopes [1, 2] and has enabled routine atomic-resolution EDS elemental mapping, as shown in Figure 1a. The breakthrough in detector technology has sparked interest in quantifying the chemical information directly from atomically resolved EDS maps [3-5]. In order to obtain an atomic-resolution EDS map, the specimen however must be tilted to a low index zone axis, resulting in different orientation with respect to each detector. This will inevitably result in different Xray signals arriving at each detector due to their different absorption distances and effective take-off angles. Such a variation could largely affect the ability to accurately quantify the overall EDS spectrum from four Super-X detectors without precautions as evidenced in this work. Therefore, understanding the X-ray signal variation from each detector under tilted specimen condition becomes both experimentally and theoretically important as a starting point for atomic-resolution EDS quantification.}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Xu, W. and Dycus, J. H. and Sang, X. and Oni, A. A. and LeBeau, J. M.}, year={2015}, month={Aug}, pages={1091–1092} }
 @article{eaton_moyer_alipour_grimley_brahlek_lebeau_engel-herbert_2015, title={Growth of SrVO3 thin films by hybrid molecular beam epitaxy}, volume={33}, ISSN={["1520-8559"]}, DOI={10.1116/1.4927439}, abstractNote={The authors report the growth of stoichiometric SrVO3 thin films on (LaAlO3)0.3(Sr2AlTaO6)0.7 (001) substrates using hybrid molecular beam epitaxy. This growth approach employs a conventional effusion cell to supply elemental A-site Sr and the metalorganic precursor vanadium oxytriisopropoxide (VTIP) to supply vanadium. Oxygen is supplied in its molecular form through a gas inlet. An optimal VTIP:Sr flux ratio has been identified using reflection high-energy electron-diffraction, x-ray diffraction, atomic force microscopy, and scanning transmission electron microscopy, demonstrating stoichiometric SrVO3 films with atomically flat surface morphology. Away from the optimal VTIP:Sr flux, characteristic changes in the crystalline structure and surface morphology of the films were found, enabling identification of the type of nonstoichiometry. For optimal VTIP:Sr flux ratios, high quality SrVO3 thin films were obtained with smallest deviation of the lattice parameter from the ideal value and with atomically smooth surfaces, indicative of the good cation stoichiometry achieved by this growth technique.}, number={6}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Eaton, Craig and Moyer, Jarrett A. and Alipour, Hamideh M. and Grimley, Everett D. and Brahlek, Matthew and LeBeau, James M. and Engel-Herbert, Roman}, year={2015}, month={Nov} }
 @article{dycus_harris_sang_fancher_findlay_oni_chan_koch_jones_allen_et al._2015, title={Highly Accurate Real Space Nanometrology Using Revolving Scanning Transmission Electron Microscopy}, volume={21}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927615012003}, DOI={10.1017/S1431927615012003}, abstractNote={, Accurately determining crystallography at the nanoscale provides key understanding of materials behavior. X-ray and neutron based diffraction methods provide highly accurate and precise measurements, but are typically limited in their application for nanoscale materials by poor spatial sensitivity. On the other hand, scanning transmission electron microscopy (STEM) is capable of spatial resolutions below an angstrom, making atomic scale analysis routine. Moreover, high-angle annular dark-field STEM produces images that are directly interpretable with intensities scaling to the atomic number and total number of atoms in a column [1-2]. While, real-space distance measurements are possible with STEM, the effects of thermal drift and scan distortion hinder accurate metrology. In this talk, we will combine revolving STEM (RevSTEM) with a method for scan distortion correction to show accurate and precise real space length measurements for a nanostructured Bi 2 Te 3-x Se x alloy. We will show the effects of thermal drift can be corrected via measuring the drift parameters from multiple frames in an image series [3]. B y using <100> silicon as a reference standard, we correct the effects from distortions introduced from the scan system, which can then be used for imaging samples of unknown crystallography. The atom columns in drift corrected image series are then indexed and assigned to a matrix representation, which yields information such as the lattice parameters on a unit cell-by-unit cell basis, shown in Figure 1a [4]. To validate the accuracy of the technique, samples of pure Bi 2 Te 3 and Bi 2 Se}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Dycus, J. H. and Harris, J. S. and Sang, X. and Fancher, C. M. and Findlay, S. D. and Oni, A. A. and Chan, T. E. and Koch, C. C. and Jones, J. L. and Allen, L. J. and et al.}, year={2015}, month={Aug}, pages={2245–2246} }
 @article{huang_zhou_tra_white_trappen_n'diaye_spencer_frye_cabrera_nguyen_et al._2015, title={Imaging magnetic and ferroelectric domains and interfacial spins in magnetoelectric La0.7Sr0.3MnO3/PbZr0.2Ti0.8O3 heterostructures}, volume={27}, ISSN={["1361-648X"]}, DOI={10.1088/0953-8984/27/50/504003}, abstractNote={Strong magnetoelectric coupling can occur at the interface between ferromagnetic and ferroelectric films. Similar to work on interfacial exchange bias, photoemission electron microscopy was utilized to image both magnetic and ferroelectric domains and the resulting interfacial Ti spin in the same locations of La0.7Sr0.3MnO3/PbZr0.2Ti0.8O3 heterostructures. Multiple image analysis techniques, which could be applicable for a variety of fields needing quantitative data on image switching, confirm both improved magnetic switching and an increased population of interfacial spins with increased thickness of the ultrathin La0.7Sr0.3MnO3 layer. The perpendicular orientation of the interfacial spins is also discussed. This work suggests a magnetoelectric dead layer, with reduced interfacial magnetoelectricity when thin magnetic films are present.}, number={50}, journal={JOURNAL OF PHYSICS-CONDENSED MATTER}, author={Huang, C-Y and Zhou, J. and Tra, V. T. and White, R. and Trappen, R. and N'Diaye, A. T. and Spencer, M. and Frye, C. and Cabrera, G. B. and Nguyen, V. and et al.}, year={2015}, month={Dec} }
 @article{sang_lebeau_2015, title={Inconsistent Normalized Intensities for Quantitative STEM: Detector Scans and Single Electron Counting}, volume={21}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927615006844}, DOI={10.1017/S1431927615006844}, abstractNote={STEM images placed on an absolute scale relative to the incident beam intensity have helped solve numerous materials science problems. Two normalization methods have been proposed: the detector scan (DS) method [1]}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Sang, Xiahan and LeBeau, James M.}, year={2015}, month={Aug}, pages={1211–1212} }
 @article{dycus_findlay_xu_sang_allen_lebeau_2015, title={Influence of Convergence Angle and Finite Effective Source Size for Quantitative Atomic Resolution EDXS}, volume={21}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S143192761500625X}, DOI={10.1017/S143192761500625X}, abstractNote={Recent progress in energy dispersive x-ray spectroscopy (EDS) has enabled atomic resolution chemical mapping [1] which has become an invaluable tool for chemical analysis, particularly for identifying heavy elements [2]. Although recent development of Super-X technology has enabled qualitative identification of the atoms present in an atom column, quantitative atomic resolution analysis remains an active area of development. Many contributions to the atomic resolution signal have been studied, such as thickness and tilt; however, the effects of many other parameters remain unreported.}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Dycus, J. H. and Findlay, S. D. and Xu, W. and Sang, X. and Allen, L. J. and LeBeau, J. M.}, year={2015}, month={Aug}, pages={1093–1094} }
 @article{oni_sang_raju_dumpala_broderick_kumar_sinnott_saxena_rajan_lebeau_2015, title={Large area strain analysis using scanning transmission electron microscopy across multiple images}, volume={106}, ISSN={["1077-3118"]}, DOI={10.1063/1.4905368}, abstractNote={Here, we apply revolving scanning transmission electron microscopy to measure lattice strain across a sample using a single reference area. To do so, we remove image distortion introduced by sample drift, which usually restricts strain analysis to a single image. Overcoming this challenge, we show that it is possible to use strain reference areas elsewhere in the sample, thereby enabling reliable strain mapping across large areas. As a prototypical example, we determine the strain present within the microstructure of a Ni-based superalloy directly from atom column positions as well as geometric phase analysis. While maintaining atomic resolution, we quantify strain within nanoscale regions and demonstrate that large, unit-cell level strain fluctuations are present within the intermetallic phase.}, number={1}, journal={APPLIED PHYSICS LETTERS}, author={Oni, A. A. and Sang, X. and Raju, S. V. and Dumpala, S. and Broderick, S. and Kumar, A. and Sinnott, S. and Saxena, S. and Rajan, K. and LeBeau, J. M.}, year={2015}, month={Jan} }
 @article{srinivasan_broderick_zhang_mishra_sinnott_saxena_lebeau_rajan_2015, title={Mapping Chemical Selection Pathways for Designing Multicomponent Alloys: an informatics framework for materials design}, volume={5}, ISSN={["2045-2322"]}, DOI={10.1038/srep17960}, abstractNote={Abstract}, journal={SCIENTIFIC REPORTS}, author={Srinivasan, Srikant and Broderick, Scott R. and Zhang, Ruifeng and Mishra, Amrita and Sinnott, Susan B. and Saxena, Surendra K. and LeBeau, James M. and Rajan, Krishna}, year={2015}, month={Dec} }
 @article{sang_grimley_schenk_schroeder_lebeau_2015, title={On the structural origins of ferroelectricity in HfO2 thin films}, volume={106}, ISSN={["1077-3118"]}, DOI={10.1063/1.4919135}, abstractNote={Here, we present a structural study on the origin of ferroelectricity in Gd doped HfO2 thin films. We apply aberration corrected high-angle annular dark-field scanning transmission electron microscopy to directly determine the underlying lattice type using projected atom positions and measured lattice parameters. Furthermore, we apply nanoscale electron diffraction methods to visualize the crystal symmetry elements. Combined, the experimental results provide unambiguous evidence for the existence of a non-centrosymmetric orthorhombic phase that can support spontaneous polarization, resolving the origin of ferroelectricity in HfO2 thin films.}, number={16}, journal={APPLIED PHYSICS LETTERS}, author={Sang, Xiahan and Grimley, Everett D. and Schenk, Tony and Schroeder, Uwe and LeBeau, James M.}, year={2015}, month={Apr} }
 @article{sang_grimley_schenk_schroeder_lebeau_2015, title={Origin of Ferroelectricity in Thin Film HfO2 Probed by Revolving STEM and PACBED}, volume={21}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927615004699}, DOI={10.1017/S1431927615004699}, abstractNote={Ferroelectric HfO 2 thin films have recently become compelling candidate materials to replace lead-containing ferroelectrics [1-3]. Though many efforts have sought to control HfO 2 ferroelectricity through doping and capping layer confinement, the multiphase nature of the films has limited our understanding of the governing mechanisms. Current hypotheses suggest that ferroelectricity arises in these films through a stabilized non-centrosymmetric Pca2 1 [2,4] or Pmn2 1 [4] orthorhombic phase, yet x-ray diffraction studies have been unable to unambiguously refine the space groups of the phases present due to the complex nature of the thin film structures [2]}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Sang, Xiahan and Grimley, Everett D. and Schenk, Tony and Schroeder, Uwe and LeBeau, James M.}, year={2015}, month={Aug}, pages={779–780} }
 @article{sang_grimley_niu_irving_lebeau_2015, title={Revealing Unit Cell Level Distortions in Random Oxide Solid Solutions by Scanning Transmission Electron Microscopy and the Projected Pair Distribution Function}, volume={21}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927615006984}, DOI={10.1017/S1431927615006984}, abstractNote={Picometer-scale lattice distortions critically determine a range of properties in oxide solid solutions including ferroelectricity, piezoelectricity, high temperature superconductivity}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Sang, Xiahan and Grimley, Everett D. and Niu, Changning and Irving, Douglas L. and LeBeau, James M.}, year={2015}, month={Aug}, pages={1239–1240} }
 @article{niu_zaddach_oni_sang_hurt_lebeau_koch_irving_2015, title={Spin-driven ordering of Cr in the equiatomic high entropy alloy NiFeCrCo}, volume={106}, ISSN={["1077-3118"]}, DOI={10.1063/1.4918996}, abstractNote={Spin-driven ordering of Cr in an equiatomic fcc NiFeCrCo high entropy alloy (HEA) was predicted by first-principles calculations. Ordering of Cr is driven by the reduction in energy realized by surrounding anti-ferromagnetic Cr with ferromagnetic Ni, Fe, and Co in an alloyed L12 structure. The fully Cr-ordered alloyed L12 phase was predicted to have a magnetic moment that is 36% of that for the magnetically frustrated random solid solution. Three samples were synthesized by milling or casting/annealing. The cast/annealed sample was found to have a low temperature magnetic moment that is 44% of the moment in the milled sample, which is consistent with theoretical predictions for ordering. Scanning transmission electron microscopy measurements were performed and the presence of ordered nano-domains in cast/annealed samples throughout the equiatomic NiFeCrCo HEA was identified.}, number={16}, journal={APPLIED PHYSICS LETTERS}, author={Niu, C. and Zaddach, A. J. and Oni, A. A. and Sang, X. and Hurt, J. W., III and LeBeau, J. M. and Koch, C. C. and Irving, D. L.}, year={2015}, month={Apr} }
 @article{zhou_tra_dong_trappen_marcus_jenkins_frye_wolfe_white_polisetty_et al._2015, title={Thickness dependence of La0.7Sr0.3MnO3/PbZr0.2Ti0.8O3 magnetoelectric interfaces}, volume={107}, ISSN={["1077-3118"]}, DOI={10.1063/1.4932517}, abstractNote={Magnetoelectric materials have great potential to revolutionize electronic devices due to the coupling of their electric and magnetic properties. Thickness varying La0.7Sr0.3MnO3 (LSMO)/PbZr0.2Ti0.8O3 (PZT) heterostructures were built and measured in this article by valence sensitive x-ray absorption spectroscopy. The sizing effects of the heterostructures on the LSMO/PZT magnetoelectric interfaces were investigated through the behavior of Mn valence, a property associated with the LSMO magnetization. We found that Mn valence increases with both LSMO and PZT thickness. Piezoresponse force microscopy revealed a transition from monodomain to polydomain structure along the PZT thickness gradient. The ferroelectric surface charge may change with domain structure and its effects on Mn valence were simulated using a two-orbital double-exchange model. The screening of ferroelectric surface charge increases the electron charges in the interface region, and greatly changes the interfacial Mn valence, which likely plays a leading role in the interfacial magnetoelectric coupling. The LSMO thickness dependence was examined through the combination of two detection modes with drastically different attenuation depths. The different length scales of these techniques' sensitivity to the atomic valence were used to estimate the depth dependence Mn valence. A smaller interfacial Mn valence than the bulk was found by globally fitting the experimental results.}, number={14}, journal={APPLIED PHYSICS LETTERS}, author={Zhou, Jinling and Tra, Vu Thanh and Dong, Shuai and Trappen, Robbyn and Marcus, Matthew A. and Jenkins, Catherine and Frye, Charles and Wolfe, Evan and White, Ryan and Polisetty, Srinivas and et al.}, year={2015}, month={Oct} }
 @article{jones_lebeau_nikkel_oni_dycus_cozzan_lin_chernatynskiy_nino_sinnott_et al._2015, title={Thin Films: Combined Experimental and Computational Methods Reveal the Evolution of Buried Interfaces during Synthesis of Ferroelectric Thin Films (Adv. Mater. Interfaces 10/2015)}, volume={2}, ISSN={2196-7350}, url={http://dx.doi.org/10.1002/ADMI.201570048}, DOI={10.1002/ADMI.201570048}, abstractNote={Scanning transmission electron microscopy is utilized to reveal atomic-level interactions that occur during thermal processing at thin film oxide-metal interfaces, as described by J. L. Jones and co-workers in article 1500181. These observations, combined with in situ X-ray diffraction and theoretical techniques, are used to determine how solution-processed lead zirconate titanate (PZT) films nucleate on Pt electrodes, results that will guide future ferroelectric film processing.}, number={10}, journal={Advanced Materials Interfaces}, publisher={Wiley}, author={Jones, Jacob L. and LeBeau, James M. and Nikkel, Jason and Oni, Adedapo A. and Dycus, J. Houston and Cozzan, Clayton and Lin, Fang-Yin and Chernatynskiy, Aleksandr and Nino, Juan C. and Sinnott, Susan B. and et al.}, year={2015}, month={Jul}, pages={n/a-n/a} }
 @article{grimley_sang_lebeau_2014, title={Application of the Projective Standard Deviation to STEM Imaging and Analysis}, volume={20}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927614002311}, DOI={10.1017/S1431927614002311}, abstractNote={The radon transformation has demonstrated tremendous utility for the processing of tomographic reconstructions, though it remains largely unapplied to problems of imaging in scanning transmission electron microscopy (STEM). A complete radon transformation projects image intensities onto lines oriented at different angles relative to the image. When orientated normal to a lattice vector, the projection becomes dominated by the intensity fluctuations determined by the interplanar spacing, as seen in the red trace in Figure 1. Projections away from these conditions result in flatter intensities as shown in the black trace in Figure 1. The standard deviation of these projected intensities thus scales with the degree to which an angle corresponds to a lattice vector. We have recently shown that the standard deviation of the normalized radon transformation as a function of angle, herein called the projective standard deviation (PSD), serves as a critical tool to enable the elimination of drift related distortions using the revolving-STEM (RevSTEM) method [1]. Furthermore, its utility extends far beyond the RevSTEM method.}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Grimley, Everett D. and Sang, Xiahan and LeBeau, James M.}, year={2014}, month={Aug}, pages={118–119} }
 @article{sang_oni_lebeau_2014, title={Atom Column Indexing: Atomic Resolution Image Analysis Through a Matrix Representation}, volume={20}, ISSN={["1435-8115"]}, DOI={10.1017/s1431927614013506}, abstractNote={Abstract}, number={6}, journal={MICROSCOPY AND MICROANALYSIS}, author={Sang, Xiahan and Oni, Adedapo A. and LeBeau, James M.}, year={2014}, month={Dec}, pages={1764–1771} }
 @article{dumpala_oni_padalkar_broderick_lebeau_rajan_2014, title={Correlative Imaging of Stacking Faults using Atom Probe Tomography (APT) and Scanning Transmission Electron Microscopy (STEM)}, volume={20}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927614006709}, DOI={10.1017/S1431927614006709}, abstractNote={Doping in Ni3Al alloy systems can have a significant enhancement in various properties including high temperature strength, fatigue and creep. The enhanced high temperature mechanical properties of Ni-based superalloys are attributed to microstructure consisting of γ’ matrix strengthened by ordered γ’ precipitates [1]. Segregation or partitioning of the doping elements in these two phases plays a vital role in mechanical properties. Thus correlative atomistic scale chemical imaging techniques are developed for better understanding of these microstructural changes and their effect on the properties. Experimental analyses of STEM and APT microscopy have been performed on Ni-based alloys. The Ni-Al-Cr system showed interesting behavior, with the STEM and atomic-resolution EDS results clearly imaging stacking faults and segregation behavior of the Cr to the disordered phase. The elemental maps of the superalloy in the γ’ show that Al and Cr occupy the same atomic column. Correlative APT studies were performed where Cr segregation was observed in agreement with STEM data. From the APT reconstructed image, it is also noticed that Al and Cr occupy similar positions. By capturing the same microstructural changes and chemical segregation between APT and STEM, we now have developed an enhanced approach for correlative microscopy, linking the structural and defect analyses of STEM with chemical analysis at the interface with APT.}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Dumpala, S. and Oni, A. A. and Padalkar, S. and Broderick, S.R. and LeBeau, J. M. and Rajan, K.}, year={2014}, month={Aug}, pages={996–997} }
 @article{oni_sang_kumar_raju_srinivasan_sinnott_saxena_rajan_lebeau_2014, title={Direct Lattice Parameter Measurements Using HAADF-STEM}, volume={20}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927614006977}, DOI={10.1017/S1431927614006977}, abstractNote={. Lattice strain is generated in crystal structures as a result of atomic size differences between host atom and solute elements during substitutional alloying. Extensive work has been performed to study lattice parameter variation with alloying elements, primarily using diffraction methods. The global information provided by reciprocal space analysis, however, limits access to local structural details. In contrast, atomic resolution STEM enables direct imaging of the crystal structure, but drift distortion currently limits capabilities to measure lattice parameters. This is particularly relevant for Ni-based superalloys as the microstructure consists of cuboidal intermetallic γ ’ phase precipitate (L1 2 structure) within a γ phase matrix (FCC structure). As the coherent γ/ γ ’ interface is responsible for limiting dislocation motion [1], direct measurement of lattice parameters and strain provides critical information to further next generation alloy design. In this presentation, we will report direct lattice parameter measurements in annealed single-crystal Ni-based superalloys using a probe-corrected scanning transmission electron microscope (FEI Titan 60-300 S/TEM). We will show that picometer precision and accuracy are enabled by the newly developed RevSTEM technique [2]. Peak locations are determined using a normalized cross correlation approach and 2D Gaussian peak fitting [2] to enable the measurement of atom column separations. RevSTEM-processed HAADF-STEM images for pure Ni 3 Al, γ ’ phase NiAlCr and γ phase NiAlCr in the <100> projection are shown in Figure 1. A histogram of the third and fourth nearest-neighbor distances calculated from the HAADF-STEM images is presented in Figure 2. The lattice parameter measurements using RevSTEM}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Oni, Adedapo A. and Sang, Xiahan and Kumar, Aakash and Raju, Selva V. and Srinivasan, Srikant and Sinnott, Susan and Saxena, Surendra and Rajan, Krishna and LeBeau, James M.}, year={2014}, month={Aug}, pages={1050–1051} }
 @article{lomenzo_zhao_takmeel_moghaddam_nishida_nelson_fancher_grimley_sang_lebeau_et al._2014, title={Ferroelectric phenomena in Si-doped HfO2 thin films with TiN and Ir electrodes}, volume={32}, number={3}, journal={Journal of Vacuum Science & Technology. B, Microelectronics and Nanometer Structures}, author={Lomenzo, P. D. and Zhao, P. and Takmeel, Q. and Moghaddam, S. and Nishida, T. and Nelson, M. and Fancher, C. M. and Grimley, E. D. and Sang, X. H. and LeBeau, J. M. and et al.}, year={2014} }
 @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{dycus_oni_sang_chan_koch_lebeau_2014, title={Observing the Interplay Between Composition and Phonon Transport in Bi2Te3-xSex Alloys using ADF STEM}, volume={20}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927614003924}, DOI={10.1017/S1431927614003924}, abstractNote={Bismuth telluride-selenide alloys are some of the most commonly used thermoelectrics at room temperature. In these materials, phonon scattering plays a pivotal role in controlling the thermoelectric properties where decoupling phonons and charge carriers induces a net heat flux that results in an electric potential. Understanding the heat flow requires knowledge of phonon scattering behavior as a function of alloying, at defects, and within the microstructure. In Bi2Te3-xSex alloys, the structure consists of stacked ‘quintuple’ layers in the sequence Te(1)-Bi-Te(2)-Bi-Te(1) [1]. Se can substitute into either the Te(1) or Te(2) sites. The position of alloying impurities in the crystal lattice greatly influences thermoelectric properties as the local bonding environment can change at different crystallographic locations. Additionally, impurities will change the bond strengths in the structure, further affecting phonon transport. Determining impurity site preference and influence on bonding thus provides a critical piece of the puzzle needed to completely understand the relationship between alloy content and properties.}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Dycus, J. H. and Oni, A. and Sang, X. and Chan, T. and Koch, C. and LeBeau, J. M.}, year={2014}, month={Aug}, pages={440–441} }
 @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{sang_grimley_niu_irving_lebeau_2014, title={Putting a New Spin on Scanning Transmission Electron Microscopy}, volume={20}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927614002426}, DOI={10.1017/S1431927614002426}, abstractNote={Local atomic scale ordering and structural distortions can significantly modify material properties. Aberration correction dramatically improves spatial resolution into the sub-Angstrom regime, unlocking information about material defects previously beyond reach. While STEM has proven essential to the atomic scale characterization of materials, for example at defects, interfaces, or even in perfect crystals, measurement of atomic displacements and distances has remained challenging due to the presence of sample drift. Distortion proportional to the rate of sample drift during image acquisition hinders the accurate measurement or even representation of atomic structure. Though modern STEM installations are optimized to reduce vibration, air flow/fields, and temperature fluctuations, sample drift generally remains.}, number={S3}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Sang, Xiahan and Grimley, Everett D. and Niu, Changning and Irving, Douglas L. and LeBeau, James M.}, year={2014}, month={Aug}, pages={140–141} }
 @article{parish_white_lebeau_miller_2014, title={Response of nanostructured ferritic alloys to high-dose heavy ion irradiation}, volume={445}, ISSN={["1873-4820"]}, DOI={10.1016/j.jnucmat.2013.11.002}, abstractNote={Abstract A latest-generation aberration-corrected scanning/transmission electron microscope (STEM) is used to study heavy-ion-irradiated nanostructured ferritic alloys (NFAs). Results are presented for STEM X-ray mapping of NFA 14YWT irradiated with 10 MeV Pt to 16 or 160 dpa at −100 °C and 750 °C, as well as pre-irradiation reference material. Irradiation at −100 °C results in ballistic destruction of the beneficial microstructural features present in the pre-irradiated reference material, such as Ti–Y–O nanoclusters (NCs) and grain boundary (GB) segregation. Irradiation at 750 °C retains these beneficial features, but indicates some coarsening of the NCs, diffusion of Al to the NCs, and a reduction of the Cr–W GB segregation (or solute excess) content. Ion irradiation combined with the latest-generation STEM hardware allows for rapid screening of fusion candidate materials and improved understanding of irradiation-induced microstructural changes in NFAs.}, number={1-3}, journal={JOURNAL OF NUCLEAR MATERIALS}, author={Parish, Chad M. and White, Ryan M. and LeBeau, James M. and Miller, Michael K.}, year={2014}, month={Feb}, pages={251–260} }
 @article{sang_lebeau_2014, title={Revolving scanning transmission electron microscopy: Correcting sample drift distortion without prior knowledge}, volume={138}, ISSN={["1879-2723"]}, DOI={10.1016/j.ultramic.2013.12.004}, abstractNote={We report the development of revolving scanning transmission electron microscopy--RevSTEM--a technique that enables characterization and removal of sample drift distortion from atomic resolution images without the need for a priori crystal structure information. To measure and correct the distortion, we acquire an image series while rotating the scan coordinate system between successive frames. Through theory and experiment, we show that the revolving image series captures the information necessary to analyze sample drift rate and direction. At atomic resolution, we quantify the image distortion using the projective standard deviation, a rapid, real-space method to directly measure lattice vector angles. By fitting these angles to a physical model, we show that the refined drift parameters provide the input needed to correct distortion across the series. We demonstrate that RevSTEM simultaneously removes the need for a priori structure information to correct distortion, leads to a dramatically improved signal-to-noise ratio, and enables picometer precision and accuracy regardless of drift rate.}, journal={ULTRAMICROSCOPY}, author={Sang, Xiahan and LeBeau, James M.}, year={2014}, month={Mar}, pages={28–35} }
 @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{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{lebeau_findlay_2013, title={Addressing Detector Non-Uniformity in Scanning Transmission Electron Microscopy}, volume={19}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927613004996}, DOI={10.1017/S1431927613004996}, 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={LeBeau, J.M. and Findlay, S.D.}, year={2013}, month={Aug}, pages={600–601} }
 @article{sarac_anderson_pearce_railsback_oni_white_hensley_lebeau_melechko_tracy_2013, title={Airbrushed Nickel Nanoparticles for Large-Area Growth of Vertically Aligned Carbon Nanofibers on Metal (Al, Cu, Ti) Surfaces}, volume={5}, ISSN={["1944-8244"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000330016500022&KeyUID=WOS:000330016500022}, DOI={10.1021/am401889t}, abstractNote={Vertically aligned carbon nanofibers (VACNFs) were grown by plasma-enhanced chemical vapor deposition (PECVD) using Ni nanoparticle (NP) catalysts that were deposited by airbrushing onto Si, Al, Cu, and Ti substrates. Airbrushing is a simple method for depositing catalyst NPs over large areas that is compatible with roll-to-roll processing. The distribution and morphology of VACNFs are affected by the airbrushing parameters and the composition of the metal foil. Highly concentrated Ni NPs in heptane give more uniform distributions than pentane and hexanes, resulting in more uniform coverage of VACNFs. For VACNF growth on metal foils, Si micropowder was added as a precursor for Si-enriched coatings formed in situ on the VACNFs that impart mechanical rigidity. Interactions between the catalyst NPs and the metal substrates impart control over the VACNF morphology. Growth of carbon nanostructures on Cu is particularly noteworthy because the miscibility of Ni with Cu poses challenges for VACNF growth, and carbon nanostructures anchored to Cu substrates are desired as anode materials for Li-ion batteries and for thermal interface materials.}, number={18}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Sarac, Mehmet F. and Anderson, Bryan D. and Pearce, Ryan C. and Railsback, Justin G. and Oni, Adedapo A. and White, Ryan M. and Hensley, Dale K. and LeBeau, James M. and Melechko, Anatoli V. and Tracy, Joseph B.}, year={2013}, month={Sep}, pages={8955–8960} }
 @article{mohammad alipour_white_eaton_moyer_engel-herbret_lebeau_2013, title={Atomic Structure and Chemistry of Defects in non-stoichiometric SrVO3 Thin Films}, volume={19}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927613008027}, DOI={10.1017/S1431927613008027}, 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={Mohammad Alipour, H. and White, R.M. and Eaton, C. and Moyer, J.A. and Engel-Herbret, R. and LeBeau, J.M.}, year={2013}, month={Aug}, pages={1206–1207} }
 @article{dycus_white_pierce_venkatasubramanian_lebeau_2013, title={Atomic scale structure and chemistry of Bi2Te3/GaAs interfaces grown by metallorganic van der Waals epitaxy}, volume={102}, ISSN={["0003-6951"]}, DOI={10.1063/1.4793518}, abstractNote={Here, we report the atomic scale structure and chemistry of epitaxial Bi2Te3 thin films grown via metallorganic chemical vapor deposition on (001) GaAs substrates. Using aberration corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF STEM), we report an atomically abrupt interface spanned by a second phase. Further, we demonstrate that interpretation of HAADF STEM image intensities does not provide an unambiguous interface structure. Combining atomic resolution imaging and spectroscopy, we determine the identity of the interfacial species is found to be consistent with that of a bilayer of Ga–Te that terminates GaAs dangling bonds.}, number={8}, journal={APPLIED PHYSICS LETTERS}, author={Dycus, J. Houston and White, Ryan M. and Pierce, Jonathan M. and Venkatasubramanian, Rama and LeBeau, James M.}, year={2013}, month={Feb} }
 @article{chan_lebeau_venkatasubramanian_thomas_stuart_koch_2013, title={Carrier concentration modulation by hot pressing pressure in n-type nanostructured Bi(Se)Te alloy}, volume={103}, ISSN={["1077-3118"]}, DOI={10.1063/1.4823801}, abstractNote={We demonstrate experimentally that an optimal hot pressing pressure is required for high thermoelectric power factor in different n-type Bi(Se)Te alloys for a given processing temperature. This phenomenon is attributed to the variations in carrier concentration, which changes the Seebeck coefficient and therefore the power factor. The variations could arise from the difference in the concentration of charged antisite defects as their formation energy changes with pressures. Furthermore, modifications of the energy gap resulting from the lattice distortions at high pressure also likely play a role.}, number={14}, journal={APPLIED PHYSICS LETTERS}, author={Chan, Tsung-ta E. and LeBeau, James M. and Venkatasubramanian, Rama and Thomas, Peter and Stuart, Judy and Koch, Carl C.}, year={2013}, month={Sep} }
 @article{oni_white_sarac_anderson_pearce_railsback_hensley_melechko_tracy_lebeau_2013, title={Chemical Analysis of Airbrushed Nickel Nanoparticles for Large-Area Growth of Vertically Aligned Carbon Nanofibers on Metal Surfaces}, volume={19}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927613009859}, DOI={10.1017/S1431927613009859}, 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={Oni, A. and White, R. and Sarac, M. and Anderson, B. and Pearce, R. and Railsback, J. and Hensley, D. and Melechko, A. and Tracy, J. and LeBeau, J.}, year={2013}, month={Aug}, pages={1572–1573} }
 @article{findlay_lebeau_2013, title={Detector non-uniformity in scanning transmission electron microscopy}, volume={124}, ISSN={["0304-3991"]}, DOI={10.1016/j.ultramic.2012.09.001}, abstractNote={A non-uniform response across scanning transmission electron microscope annular detectors has been found experimentally, but is seldom incorporated into simulations. Through case study simulations, we establish the nature and scale of the discrepancies which may arise from failing to account for detector non-uniformity. If standard detectors are used at long camera lengths such that the detector is within or near to the bright field region, we find errors in contrast of the order of 10%, sufficiently small for qualitative work but non-trivial as experiments become more quantitative. In cases where the detector has been characterized in advance, we discuss the detector response normalization and how it may be incorporated in simulations.}, journal={ULTRAMICROSCOPY}, author={Findlay, S. D. and LeBeau, J. M.}, year={2013}, month={Jan}, pages={52–60} }
 @article{wilson_sun_chi_white_lebeau_lamb_wiley_2013, title={From Core-Shell to Alloys: The Preparation and Characterization of Solution-Synthesized AuPd Nanoparticle Catalysts}, volume={117}, ISSN={["1932-7447"]}, DOI={10.1021/jp404157m}, abstractNote={This article describes the solution-phase synthesis of 4 nm gold nanoparticles with 0.7 atom-thick, 1.9 atom-thick, and 3.8 atom-thick layers of Pd on their surfaces. These well-defined core–shell nanoparticles were deposited on a silica support, calcined, and reduced at 300 °C to create alloyed nanoparticles containing 10.9, 20.2, and 28.5% Pd (w/w). Monometallic Pd nanoparticles sintered during calcination at 300 °C, but no sintering was observed for AuPd nanoparticles. Diffuse reflectance infrared Fourier transform (DRIFT) spectra of adsorbed CO suggests that Au donates d electron density to Pd in the core–shell and alloy structures and confirms the presence of Au and Pd atoms on the surface of the nanoparticles after calcination and reduction. The properties of the AuPd alloy catalysts were tested in the vapor-phase conversion of α-limonene to p-cymene. AuPd nanoparticles containing 20% or more Pd per particle produced p-cymene yields greater than 80%, equivalent to conventional Pd catalysts prepared ...}, number={34}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Wilson, Adria R. and Sun, Keyi and Chi, Miaofang and White, Ryan M. and LeBeau, James M. and Lamb, H. Henry and Wiley, Benjamin J.}, year={2013}, month={Aug}, pages={17557–17566} }
 @article{samberg_alipour_bradshaw_carlin_colter_lebeau_el-masry_bedair_2013, title={Interface properties of Ga(As,P)/(In,Ga)As strained multiple quantum well structures}, volume={103}, ISSN={["0003-6951"]}, DOI={10.1063/1.4818548}, abstractNote={(In,Ga)As/Ga(As,P) multiple quantum wells (MQWs) with GaAs interface layers have been characterized with photoluminescence (PL) and high resolution scanning transmission electron microscopy (STEM). By growing (In,Ga)As/Ga(As,P) MQWs with asymmetric GaAs interfacial layers, we found that phosphorus carry-over had a profound effect on the absorption edge of the (In,Ga)As wells. Evidence for this phosphorus was initially determined via PL and then definitively proven through STEM and energy dispersive x-ray spectroscopy. We show that the phosphorus carry-over can be prevented with sufficiently thick GaAs transition layers. Preliminary results for GaAs p-i-n solar cells utilizing the improved MQWs are presented.}, number={7}, journal={APPLIED PHYSICS LETTERS}, author={Samberg, Joshua P. and Alipour, Hamideh M. and Bradshaw, Geoffrey K. and Carlin, C. Zachary and Colter, Peter C. and LeBeau, James M. and El-Masry, N. A. and Bedair, Salah M.}, year={2013}, month={Aug} }
 @article{parish_white_lebeau_zhang_miller_2013, title={Multi-detector STEM-EDS mapping of ion-irradiated nanostructured ferritic alloys}, volume={19}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S143192761300771X}, DOI={10.1017/S143192761300771X}, 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={Parish, C. and White, R.M. and LeBeau, J.M. and Zhang, Y. and Miller, M.K.}, year={2013}, month={Aug}, pages={1144–1145} }
 @article{ruben_cosgriff_d'alfonso_findlay_lebeau_allen_2012, title={Interface location by depth sectioning using a low-angle annular dark field detector}, volume={113}, ISSN={0304-3991}, url={http://dx.doi.org/10.1016/j.ultramic.2011.11.002}, DOI={10.1016/j.ultramic.2011.11.002}, abstractNote={We investigate the application of a highly convergent aberration-corrected electron probe to the determination of depth-related features of layered heterostructures. By centring the probe upon an atomic column and varying defocus, we obtain a depth-scan of the signal from a low-angle annular dark field (LAADF) detector. Peaks associated with the heterojunctions and crystal surfaces are observed which allow for the sample thickness and heterojunction locations to be determined. Channelling of the electron wave function along atomic columns is shown to play an important role in the production of these peaks, whose presence at all interfaces is shown to rely on a combination of elastic and thermal diffuse scattering signals.}, journal={Ultramicroscopy}, publisher={Elsevier BV}, author={Ruben, Gary and Cosgriff, Eireann C. and D'Alfonso, Adrian J. and Findlay, Scott D. and LeBeau, James M. and Allen, Leslie J.}, year={2012}, month={Feb}, pages={131–138} }
 @article{lebeau_findlay_allen_stemmer_2012, title={Quantitative STEM: Experimental Methods and Applications}, volume={371}, ISSN={["1742-6596"]}, DOI={10.1088/1742-6596/371/1/012053}, abstractNote={High-angle annular dark-field (HAADF) imaging in scanning transmission electron microscopy (STEM) is highly sensitive to both the atomic number and the Debye-Waller factor of the atom columns. We will discuss the experimental requirements for a quantitative understanding of STEM image contrast, in particular the determination of the precise specimen thickness. We show that near perfect agreement can be achieved between theory and experiment and demonstrate that quantitative STEM allows for column-by-column counting of all the atoms in an arbitrarily shaped specimen.}, journal={ELECTRON MICROSCOPY AND ANALYSIS GROUP CONFERENCE 2011 (EMAG 2011)}, author={LeBeau, J. M. and Findlay, S. D. and Allen, L. J. and Stemmer, S.}, year={2012} }
 @article{hwang_chobpattana_zhang_lebeau_engel-herbert_stemmer_2011, title={Al-doped HfO2/In0.53Ga0.47As metal-oxide-semiconductor capacitors}, volume={98}, ISSN={["1077-3118"]}, DOI={10.1063/1.3575569}, abstractNote={Hafnium oxide gate dielectrics doped with a one to two percent of aluminum are grown on In0.53Ga0.47As channels by codeposition of trimethylaluminum (TMA) and hafnium tertbutoxide (HTB). It is shown that the addition of TMA during growth allows for smooth, amorphous films that can be scaled to ∼5 nm physical thickness. Metal-oxide-semiconductor capacitors (MOSCAPs) with this dielectric have an equivalent oxide thickness of 1 nm, show an unpinned, efficient Fermi level movement and lower interface trap densities than MOSCAPs with HfO2 dielectrics grown by sequential TMA/HTB deposition.}, number={14}, journal={APPLIED PHYSICS LETTERS}, author={Hwang, Yoontae and Chobpattana, Varistha and Zhang, Jack Y. and LeBeau, James M. and Engel-Herbert, Roman and Stemmer, Susanne}, year={2011}, month={Apr} }
 @article{lebeau_d'alfonso_allen_stemmer_2011, title={Determination of Thin-Film Ferroelectric Polarity at the Nanoscale}, volume={17}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927611007707}, DOI={10.1017/S1431927611007707}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in  Nashville, Tennessee, USA, August 7–August 11, 2011.}, number={S2}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={LeBeau, J and D'Alfonso, A and Allen, L and Stemmer, S}, year={2011}, month={Jul}, pages={1366–1367} }
 @article{lebeau_d’alfonso_wright_allen_stemmer_2011, title={Determining ferroelectric polarity at the nanoscale}, volume={98}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.3549300}, DOI={10.1063/1.3549300}, abstractNote={Position averaged convergent beam electron diffraction (PACBED) in scanning transmission electron microscopy is shown to be capable of determining the direction of ferroelectric polarity at the nanoscale. We show that PACBED patterns of ferroelectric materials such as PbTiO3 and BaTiO3 are sensitive to both unit cell distortion and the absolute direction of polarity within the unit cell. It is shown that the polarity can be determined even in cases where real-space high-resolution transmission electron microscopy would not be capable of resolving the atomic displacements. The method is applied to determine the direction of polarization in an epitaxial BaTiO3 film.}, number={5}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={LeBeau, James M. and D’Alfonso, Adrian J. and Wright, Nicholas J. and Allen, Leslie J. and Stemmer, Susanne}, year={2011}, month={Jan}, pages={052904} }
 @article{zhang_lebeau_d'alfonso_allen_stemmer_2011, title={Exploring the Strain Sensitivity of Image Contrast in Quantitative STEM of SrTiO3}, volume={17}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927611007422}, DOI={10.1017/S1431927611007422}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in  Nashville, Tennessee, USA, August 7–August 11, 2011.}, number={S2}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Zhang, J and LeBeau, J and D'Alfonso, A and Allen, L and Stemmer, S}, year={2011}, month={Jul}, pages={1310–1311} }
 @article{xie_mita_hussey_rice_tweedie_lebeau_collazo_sitar_2011, title={On the strain in n-type GaN}, volume={99}, ISSN={["0003-6951"]}, DOI={10.1063/1.3647772}, abstractNote={It was demonstrated that Ge has the same effect as Si on the strain evolution in n-type GaN as measured by x-ray diffraction. Dislocation inclination, which causes tensile strain in n-type GaN, was clearly observed by transmission electron microscopy where Ge doping was introduced during epitaxial growth. This result is explained by the Fermi level effect model that indicates dislocation inclination due to the climbing process through Ga vacancies. Therefore, there is no dependence of dislocation inclination on dopant species.}, number={14}, journal={APPLIED PHYSICS LETTERS}, author={Xie, Jinqiao and Mita, Seiji and Hussey, Lindsay and Rice, Anthony and Tweedie, James and LeBeau, James and Collazo, Ramon and Sitar, Zlatko}, year={2011}, month={Oct} }
 @article{lebeau_findlay_allen_stemmer_2011, title={Standardless Atom Counting in Scanning Transmission Electron Microscopy}, volume={11}, ISSN={1530-6984 1530-6992}, url={http://dx.doi.org/10.1021/nl1042215}, DOI={10.1021/nl1042215}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionORIGINAL ARTICLEThis notice is a correctionStandardless Atom Counting in Scanning Transmission Electron MicroscopyJames M. LeBeau, Scott D. Findlay, Leslie J. Allen, and Susanne Stemmer*Cite this: Nano Lett. 2011, 11, 1, 310Publication Date (Web):December 10, 2010Publication History Received3 December 2010Published online10 December 2010Published inissue 12 January 2011https://doi.org/10.1021/nl1042215Copyright © 2010 American Chemical SocietyRequest reuse permissions This publication is free to access through this site. Learn MoreArticle Views1070Altmetric-Citations3LEARN 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 InReddit PDF (60 KB) Get e-AlertscloseSUBJECTS:Gold,Scanning transmission electron microscopy Get e-Alerts}, number={1}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={LeBeau, James M. and Findlay, Scott D. and Allen, Leslie J. and Stemmer, Susanne}, year={2011}, month={Jan}, pages={310–310} }
 @article{forbes_d'alfonso_findlay_van dyck_lebeau_stemmer_allen_2011, title={Thermal diffuse scattering in transmission electron microscopy}, volume={111}, ISSN={["1879-2723"]}, DOI={10.1016/j.ultramic.2011.09.017}, abstractNote={In conventional transmission electron microscopy, thermal scattering significantly affects the image contrast. It has been suggested that not accounting for this correctly is the main cause of the Stobbs factor, the ubiquitous, large contrast mismatch found between theory and experiment. In the case where a hard aperture is applied, we show that previous conclusions drawn from work using bright field scanning transmission electron microscopy and invoking the principle of reciprocity are reliable in the presence of thermal scattering. In the aperture-free case it has been suggested that even the most sophisticated mathematical models for thermal diffuse scattering lack in their numerical implementation, specifically that there may be issues in sampling, including that of the contrast transfer function of the objective lens. We show that these concerns can be satisfactorily overcome with modest computing resources; thermal scattering can be modelled accurately enough for the purpose of making quantitative comparison between simulation and experiment. Spatial incoherence of the source is also investigated. Neglect or inadequate handling of thermal scattering in simulation can have an appreciable effect on the predicted contrast and can be a significant contribution to the Stobbs factor problem.}, number={12}, journal={ULTRAMICROSCOPY}, author={Forbes, B. D. and D'Alfonso, A. J. and Findlay, S. D. and Van Dyck, D. and LeBeau, J. M. and Stemmer, S. and Allen, L. J.}, year={2011}, month={Dec}, pages={1670–1680} }
 @article{son_lebeau_allen_stemmer_2010, title={Conductivity enhancement of ultrathin LaNiO3 films in superlattices}, volume={97}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.3511738}, DOI={10.1063/1.3511738}, abstractNote={The resistance of superlattices composed of bilayers of ultrathin (∼4 unit cells) of LaNiO3 and ∼3 unit cells of insulating SrTiO3 is explored as a function of temperature and the number of bilayers. All superlattices with more than one bilayer are metallic, whereas a single bilayer is insulating. Two possible interpretations of the electrical characteristics of the superlattices are discussed. The first model involves conduction in parallel-connected layers, whereas the second model assumes coupling of layers, each of which is near the percolation threshold for a metal-insulator transition.}, number={20}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Son, Junwoo and LeBeau, James M. and Allen, S. James and Stemmer, Susanne}, year={2010}, month={Nov}, pages={202109} }
 @article{buehl_lebeau_stemmer_scarpulla_palmstrøm_gossard_2010, title={Growth of embedded ErAs nanorods on (411)A and (411)B GaAs by molecular beam epitaxy}, volume={312}, ISSN={0022-0248}, url={http://dx.doi.org/10.1016/j.jcrysgro.2010.04.031}, DOI={10.1016/j.jcrysgro.2010.04.031}, abstractNote={The low solubility of Er in GaAs results in the formation of ErAs nanostructures when GaAs is grown with 5–6 at% Er/Ga ratio by molecular beam epitaxy on GaAs surfaces. For growth on the (4 1 1)A GaAs surface, cross-sectional scanning transmission electron microscopy images show the presence of ErAs nanorods embedded in a GaAs matrix extending along the [2 1 1] direction with a spacing of roughly 7 nm and a diameter of roughly 2 nm. Growth on the GaAs (4 1 1)B surface resulted in only nanoparticle formation. Variation of the polarized optical absorption with in-plane polarization angle is consistent with coupling to surface plasmon resonances of the semimetallic nanostructures.}, number={14}, journal={Journal of Crystal Growth}, publisher={Elsevier BV}, author={Buehl, Trevor E. and LeBeau, James M. and Stemmer, Susanne and Scarpulla, Michael A. and Palmstrøm, Christopher J. and Gossard, Arthur C.}, year={2010}, month={Jul}, pages={2089–2092} }
 @article{son_moetakef_lebeau_ouellette_balents_allen_stemmer_2010, title={Low-dimensional Mott material: Transport in ultrathin epitaxial LaNiO3 films}, volume={96}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.3309713}, DOI={10.1063/1.3309713}, abstractNote={Electrical resistivity and magnetotransport are explored for thin (3–30 nm), epitaxial LaNiO3 films. Films were grown on three different substrates to obtain LaNiO3 films that are coherently strained, with different signs and magnitude of film strain. It is shown that d-band transport is inhibited as the layers progress from compression to tension. The Hall coefficient is “holelike.” Increasing tensile strain causes the film resistivity to increase, causing strong localization to appear below a critical thickness.}, number={6}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Son, Junwoo and Moetakef, Pouya and LeBeau, James M. and Ouellette, Daniel and Balents, Leon and Allen, S. James and Stemmer, Susanne}, year={2010}, month={Feb}, pages={062114} }
 @article{lebeau_findlay_allen_stemmer_2010, title={Position averaged convergent beam electron diffraction: Theory and applications}, volume={110}, ISSN={0304-3991}, url={http://dx.doi.org/10.1016/j.ultramic.2009.10.001}, DOI={10.1016/j.ultramic.2009.10.001}, abstractNote={A finely focused angstrom-sized coherent electron probe produces a convergent beam electron diffraction pattern composed of overlapping orders of diffracted disks that sensitively depends on the probe position within the unit cell. By incoherently averaging these convergent beam electron diffraction patterns over many probe positions, a pattern develops that ceases to depend on lens aberrations and effective source size, but remains highly sensitive to specimen thickness, tilt, and polarity. Through a combination of experiment and simulation for a wide variety of materials, we demonstrate that these position averaged convergent beam electron diffraction patterns can be used to determine sample thicknesses (to better than 10%), specimen tilts (to better than 1 mrad) and sample polarity for the same electron optical conditions and sample thicknesses as used in atomic resolution scanning transmission electron microscopy imaging. These measurements can be carried out by visual comparison without the need to apply pattern-matching algorithms. The influence of thermal diffuse scattering on patterns is investigated by comparing the frozen phonon and absorptive model calculations. We demonstrate that the absorptive model is appropriate for measuring thickness and other specimen parameters even for relatively thick samples (>50 nm).}, number={2}, journal={Ultramicroscopy}, publisher={Elsevier BV}, author={LeBeau, James M. and Findlay, Scott D. and Allen, Leslie J. and Stemmer, Susanne}, year={2010}, month={Jan}, pages={118–125} }
 @article{lebeau_findlay_allen_stemmer_2010, title={Standardless Atom Counting in Scanning Transmission Electron Microscopy}, volume={10}, ISSN={1530-6984 1530-6992}, url={http://dx.doi.org/10.1021/nl102025s}, DOI={10.1021/nl102025s}, abstractNote={We demonstrate that high-angle annular dark-field imaging in scanning transmission electron microscopy allows for quantification of the number and location of all atoms in a three-dimensional, crystalline, arbitrarily shaped specimen without the need for a calibration standard. We show that the method also provides for an approach to directly measure the finite effective source size of a scanning transmission electron microscope.}, number={11}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={LeBeau, James M. and Findlay, Scott D. and Allen, Leslie J. and Stemmer, Susanne}, year={2010}, month={Nov}, pages={4405–4408} }
 @article{stemmer_lebeau_findlay_d'alfonso_allen_2010, title={Towards Quantitative Analysis of STEM Image Contrast of Interfaces and Surfaces}, volume={16}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927610061684}, DOI={10.1017/S1431927610061684}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.}, number={S2}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Stemmer, S and LeBeau, JM and Findlay, SD and D'Alfonso, AJ and Allen, LJ}, year={2010}, month={Jul}, pages={1472–1473} }
 @article{bougeard_sircar_ahlers_lang_abstreiter_trampert_lebeau_stemmer_saxey_cerezo_2009, title={Ge1-xMnxClusters: Central Structural and Magnetic Building Blocks of Nanoscale Wire-Like Self-Assembly in a Magnetic Semiconductor}, volume={9}, ISSN={1530-6984 1530-6992}, url={http://dx.doi.org/10.1021/nl901928f}, DOI={10.1021/nl901928f}, abstractNote={Controlled nanoscale self-assembly of magnetic entities in semiconductors opens novel perspectives for the tailoring of magnetic semiconductor films and nanostructures with room temperature functionality. We report that a strongly directional self-assembly in growth direction in Mn-alloyed Ge is due to a stacking of individual Ge(1-x)Mn(x) clusters. The clusters represent the relevant entities for the magnetization of the material. They are formed of a core-shell structure displaying a Mn concentration gradient. While the magnetic moments seem to be carried by the shells of the clusters, their core is magnetically inactive.}, number={11}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={Bougeard, D. and Sircar, N. and Ahlers, S. and Lang, V. and Abstreiter, G. and Trampert, A. and LeBeau, J. M. and Stemmer, S. and Saxey, D. W. and Cerezo, A.}, year={2009}, month={Nov}, pages={3743–3748} }
 @article{lebeau_findlay_allen_stemmer_2009, title={Position Averaged Convergent Beam Electron Diffraction}, volume={15}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927609096743}, DOI={10.1017/S1431927609096743}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009}, number={S2}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={LeBeau, J and Findlay, S and Allen, L and Stemmer, S}, year={2009}, month={Jul}, pages={494–495} }
 @article{lebeau_findlay_wang_jacobson_allen_stemmer_2009, title={Quantitative HAADF Imaging of Crystals Containing Heavy Elements: A Comparison with Theory}, volume={15}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S143192760909521X}, DOI={10.1017/S143192760909521X}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009}, number={S2}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={LeBeau, J and Findlay, S and Wang, X and Jacobson, A and Allen, L and Stemmer, S}, year={2009}, month={Jul}, pages={466–467} }
 @article{lebeau_engel-herbert_jalan_cagnon_moetakef_stemmer_stephenson_2009, title={Stoichiometry optimization of homoepitaxial oxide thin films using x-ray diffraction}, volume={95}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.3243696}, DOI={10.1063/1.3243696}, abstractNote={Homoepitaxial SrTiO3 thin films grown by molecular beam epitaxy are analyzed using high-resolution x-ray diffraction and transmission electron microscopy. Measured 00L x-ray scans from stoichiometric and nonstoichiometric films are compared with calculations that account for the effects of film thickness, lattice parameter, fractional site occupancy, and an offset between film and substrate at the interface. It is found that thickness fringes, commonly observed around Bragg reflections even in stoichiometric homoepitaxial SrTiO3 films, arise from a film/substrate interface offset. Transmission electron microscopy studies confirm the presence of strain at those homoepitaxial interfaces that show an offset in x-ray diffraction. The consequences for stoichiometry optimization of homoepitaxial films using high-resolution x-ray diffraction and the quality of regrown oxide interfaces are discussed.}, number={14}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={LeBeau, James M. and Engel-Herbert, Roman and Jalan, Bharat and Cagnon, Joël and Moetakef, Pouya and Stemmer, Susanne and Stephenson, G. Brian}, year={2009}, month={Oct}, pages={142905} }
 @article{lebeau_hu_palmstrøm_stemmer_2008, title={Atomic structure of postgrowth annealed epitaxial Fe/(001)GaAs interfaces}, volume={93}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.2990622}, DOI={10.1063/1.2990622}, abstractNote={The interfacial atomic structure of epitaxial Fe films grown by molecular beam epitaxy on c(4×4) reconstructed (001) GaAs was investigated using high-angle annular dark-field imaging in scanning transmission electron microscopy. No extended interfacial reaction phase is observed and the image contrast is discussed in terms of the interface atomic configuration. The images show an As-terminated semiconductor. The interface consists of a single partially occupied plane inserted between the Fe film and the GaAs, which most likely is occupied by Fe. This interface structure provides strong evidence for preferential Fe–As bonding across the interface.}, number={12}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={LeBeau, James M. and Hu, Qi O. and Palmstrøm, Christopher J. and Stemmer, Susanne}, year={2008}, month={Sep}, pages={121909} }
 @article{lebeau_stemmer_2008, title={Experimental quantification of annular dark-field images in scanning transmission electron microscopy}, volume={108}, ISSN={0304-3991}, url={http://dx.doi.org/10.1016/j.ultramic.2008.07.001}, DOI={10.1016/j.ultramic.2008.07.001}, abstractNote={This paper reports on a method to obtain atomic resolution Z-contrast (high-angle annular dark-field) images with intensities normalized to the incident beam. The procedure bypasses the built-in signal processing hardware of the microscope to obtain the large dynamic range necessary for consecutive measurements of the incident beam and the intensities in the Z-contrast image. The method is also used to characterize the response of the annular dark-field detector output, including conditions that avoid saturation and result in a linear relationship between the electron flux reaching the detector and its output. We also characterize the uniformity of the detector response across its entire area and determine its size and shape, which are needed as input for image simulations. We present normalized intensity images of a SrTiO3 single crystal as a function of thickness. Averaged, normalized atom column intensities and the background intensity are extracted from these images. The results from the approach developed here can be used for direct, quantitative comparisons with image simulations without any need for scaling.}, number={12}, journal={Ultramicroscopy}, publisher={Elsevier BV}, author={LeBeau, James M. and Stemmer, Susanne}, year={2008}, month={Nov}, pages={1653–1658} }
 @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{scarpulla_zide_lebeau_van de walle_gossard_delaney_2008, title={Near-infrared absorption and semimetal-semiconductor transition in 2nm ErAs nanoparticles embedded in GaAs and AlAs}, volume={92}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.2908213}, DOI={10.1063/1.2908213}, abstractNote={We report strong near-infrared absorption peaks in epitaxial films of GaAs and AlAs containing approximately 0.5–5% of the semimetal ErAs. The energy of the resonant absorption peak can be changed from 0.62to1.0eV (2.2–1.4μm) by variation of the ErAs volume fraction and the substrate temperature. We interpret the infrared absorption in terms of transitions across an energy gap caused by a confinement-induced semimetal-semiconductor transition. An effective mass model relates the changes in nanoparticle diameter observed in transmission electron microscopy to the energy gap.}, number={17}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Scarpulla, Michael A. and Zide, Joshua M. O. and LeBeau, James M. and Van de Walle, Chris G. and Gossard, Arthur C. and Delaney, Kris T.}, year={2008}, month={Apr}, pages={173116} }
 @article{lebeau_findlay_allen_stemmer_2008, title={Quantitative HAADF-STEM and EELS}, volume={14}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927608082263}, DOI={10.1017/S1431927608082263}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque,   New Mexico,   USA,   August 3 – August 7,   2008}, number={S2}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={LeBeau, JM and Findlay, SD and Allen, LJ and Stemmer, S}, year={2008}, month={Aug}, pages={1352–1353} }
 @article{allen_d'alfonso_bosman_findlay_oxley_keast_lebeau_stemmer_2008, title={Simulation of Atomic Resolution Images in STEM}, volume={14}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927608082019}, DOI={10.1017/S1431927608082019}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008}, number={S2}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Allen, LJ and D'Alfonso, AJ and Bosman, M and Findlay, SD and Oxley, MP and Keast, VJ and LeBeau, JM and Stemmer, S}, year={2008}, month={Aug}, pages={922–923} }
 @article{lebeau_jur_lichtenwalner_kingon_klenov_stemmer_2008, title={Thermal Stability of Hf-Based Gate Dielectric Stacks with Rare-Earth Oxide Capping Layers}, volume={14}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927608084109}, DOI={10.1017/S1431927608084109}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008}, number={S2}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={LeBeau, JM and Jur, JS and Lichtenwalner, DJ and Kingon, AI and Klenov, DO and Stemmer, S}, year={2008}, month={Aug}, pages={418–419} }
 @article{klenov_lebeau_zide_gossard_stemmer_2007, title={Combination of TEM and STEM to Investigate the Self-Assembly of Epitaxial Nanocomposites}, volume={13}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S1431927607077252}, DOI={10.1017/S1431927607077252}, abstractNote={Extended abstract of a paper presented at Microscopy and Microanalysis 2007 in Ft. Lauderdale, Florida, USA, August 5 – August 9, 2007}, number={S02}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={Klenov, DO and LeBeau, J and Zide, J and Gossard, AC and Stemmer, S}, year={2007}, month={Aug} }
 @article{lebeau_boonyongmaneerat_2007, title={Comparison study of aqueous binder systems for slurry-based processing}, volume={458}, ISSN={0921-5093}, url={http://dx.doi.org/10.1016/j.msea.2007.01.112}, DOI={10.1016/j.msea.2007.01.112}, abstractNote={The use of environmentally friendly alternatives, such as water, to replace volatile and toxic solvents for material forming applications has been gaining increased attention from industry in recent years. This study provides the groundwork for selecting water-compatible binders for clean slurry-based processing based on the relative performance of binders. In particular, the study examines the influence of various binders, including thermoplastic starch, polyvinyl alcohol, styrene–butadiene latex, and acrylic latex, on the properties of aqueous-based powder suspensions and pre-fired multilayer laminates fabricated using a modified dip coating process. Tungsten (W)/aluminum oxide (Al2O3), a common metal–ceramic system used in various slurry-based processes and applications, is selected as a representative material system for the study. Through the characterizations of physical properties and microstructures of the materials, the application-specific property optimization of each binder system is determined and discussed. Latexes and cross-liked PVA are found feasible for water-based processing, provided that there is proper control of processing parameters.}, number={1-2}, journal={Materials Science and Engineering: A}, publisher={Elsevier BV}, author={LeBeau, James M. and Boonyongmaneerat, Yuttanant}, year={2007}, month={Jun}, pages={17–24} }
 @article{klenov_zide_lebeau_gossard_stemmer_2007, title={Ordering of ErAs nanoparticles embedded in epitaxial InGaAs layers}, volume={90}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.2715174}, DOI={10.1063/1.2715174}, abstractNote={The authors report on the microstructures of semimetallic ErAs nanoparticles embedded in epitaxial InGaAs layers by codeposition of Er. The size of the particles (1–3nm) was approximately independent of the amount of deposited Er. At large ErAs concentrations (>3at.%), the particles showed a strong tendency to order on the {114} planes of the semiconductor matrix. The ordering was only observed along one of the ⟨110⟩ directions, likely reflecting the strong anisotropy in surface diffusion.}, number={12}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Klenov, Dmitri O. and Zide, Joshua M. O. and LeBeau, James M. and Gossard, Arthur C. and Stemmer, Susanne}, year={2007}, month={Mar}, pages={121917} }