@article{ihlefeld_daniels_aygun_borland_maria_2010, title={Property engineering in BaTiO3 films by stoichiometry control}, volume={25}, ISSN={["2044-5326"]}, DOI={10.1557/jmr.2010.0151}, abstractNote={BaTiO3 thin films were prepared on metallic foil substrates using chemical solution deposition. The impact of A to B site cation ratios on the phase assemblage and microstructural and dielectric properties was investigated by characterizing a sample set that includes stoichiometric BaTiO3 and 1, 2, 3, 4, and 5 mol% excess BaO. Each composition was subjected to a high-temperature anneal step with maximum dwell temperatures of 1000, 1100, and 1200 °C for 20 h. Excess barium concentrations greater than 3% lead to dramatic grain growth and average grain sizes exceeding 1 μm. Despite the large deviations from stoichiometry and the 20 h dwell time at temperature, x-ray diffraction, and high-resolution electron microscopy analysis were unable to detect secondary phases until films with 5% excess barium were annealed to 1200 °C. Thin films with 3% excess barium were prepared on copper substrates and annealed at 1060 °C, the practical limit for copper. This combination of BaO excess and annealing temperature produced an average lateral grain size of 0.8 μm and a room-temperature permittivity of 4000. This is in comparison to a permittivity of 1800 for stoichiometric material prepared using identical conditions. This work suggests metastable solubility of BaO in BaTiO3 that leads to enhanced grain growth and large permittivity values. This technique provides a new solid-state means of achieving grain growth in low thermal budget systems.}, number={6}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Ihlefeld, J. F. and Daniels, P. R. and Aygun, S. M. and Borland, W. J. and Maria, J-P.}, year={2010}, month={Jun}, pages={1064–1071} }
 @misc{borland_burn_ihlefeld_maria_suh_2009, title={Articles comprising manganese doped barium titanate thin film compositions}, volume={7,572,518}, number={2009 Aug. 11}, author={Borland, W. and Burn, I. and Ihlefeld, J. F. and Maria, J. P. and Suh, S.}, year={2009} }
 @misc{borland_burn_ihlefeld_maria_suh_2009, title={Methods of making thin film capacitors comprising a manganese doped barium titantate dielectric}, volume={7,601,181}, number={2009 Oct. 13}, author={Borland, W. and Burn, I. and Ihlefeld, J. F. and Maria, J. P. and Suh, S.}, year={2009} }
 @article{ihlefeld_losego_collazo_borland_maria_2008, title={Defect chemistry of nano-grained barium titanate films}, volume={43}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-007-2135-3}, number={1}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Ihlefeld, Jon F. and Losego, Mark D. and Collazo, Ramon and Borland, William J. and Maria, Jon-Paul}, year={2008}, month={Jan}, pages={38–42} }
 @article{ihlefeld_borland_maria_2008, title={Dielectric and microstructural properties of barium titanate hafhate thin films}, volume={516}, DOI={10.1016/j.tsf.2007.08.096}, abstractNote={Barium titanate hafnate (BaTi1−xHfxO3, 0 ≤ x ≤ 0.25) thin films have been deposited by a chemical solution method on copper foil substrates. The films were crystallized at 900 °C and in a reducing atmosphere to prevent substrate oxidation. Perovskite phase formation was identified for each composition, accompanied by an increased pseudocubic lattice parameter. Temperature dependent dielectric measurements revealed a decreasing phase transition temperature and peak permittivity with increasing hafnium level. The decrease in permittivity resulted from grain size reduction with increasing hafnium content. Compositions containing 25 mol% barium hafnate display a deviation from Curie–Weiss behavior indicating the onset of relaxor behavior.}, number={10}, journal={Thin Solid Films}, author={Ihlefeld, J. F. and Borland, W. J. and Maria, J. P.}, year={2008}, pages={3162–3166} }
 @article{ihlefeld_borland_maria_2008, title={Enhanced dielectric tunability in barium titanate thin films with boron additions}, volume={58}, ISSN={["1359-6462"]}, DOI={10.1016/j.scriptamat.2007.11.008}, abstractNote={Boron incorporation in 650 nm thick polycrystalline BaTiO3 films results in grain growth and dramatic dielectric response improvements. For levels between 0% and 3%, average grain size is increased from 150 to 200 nm and the maximum permittivity values are nearly doubled, with tunabilities increased to greater than 90% while maintaining high field loss tangents below 0.03. These results demonstrate a pathway for microstructure engineering and property optimization in refractory electroceramic oxide thin films without increasing the thermal budget.}, number={7}, journal={SCRIPTA MATERIALIA}, author={Ihlefeld, Jon F. and Borland, William J. and Maria, Jon-Paul}, year={2008}, month={Apr}, pages={549–552} }
 @article{ihlefeld_vodnick_baker_borland_maria_2008, title={Extrinsic scaling effects on the dielectric response of ferroelectric thin films}, volume={103}, ISSN={["1089-7550"]}, DOI={10.1063/1.2903211}, abstractNote={Scaling effects in polycrystalline ferroelectric thin films were investigated by preparing barium titanate in a manner that maintained constant composition and film thickness while allowing systematically increased grain size and crystalline coherence. The average grain dimensions ranged from 60to110nm, and temperature dependence of permittivity analysis revealed diffuse phase transitions in all cases. Maximum permittivity values ranged from 380 to 2040 for the smallest to largest sizes, respectively. Dielectric hysteresis is evident at room temperature for all materials, indicating stability of the ferroelectric phase. Comparison of permittivity values at high electric fields indicates that the intrinsic dielectric response is identical and microstructural artifacts likely have a minimal influence on film properties across the sample series. Permittivity values, however, are substantially smaller than those reported for bulk material with similar grain dimensions. X-ray line broadening measurements were taken for the grain size series at the Cornell High Energy Synchrotron Source (CHESS), which revealed coherent scattering dimensions substantially smaller than the microscopy-determined grain size. Collectively these data sets suggest that permittivity values are influenced not only by grain size but also by the mosaic structure existing within each grain, and that thin film thermal budgets, which are several hundred degrees lower than used for bulk processing, are responsible for reduced crystalline coherence, and likely the origin of degraded electromechanical response in thin film ferroelectrics.}, number={7}, journal={JOURNAL OF APPLIED PHYSICS}, author={Ihlefeld, Jon F. and Vodnick, Aaron M. and Baker, Shefford P. and Borland, William J. and Maria, Jon-Paul}, year={2008}, month={Apr} }
 @article{laughlin_ihlefeld_daniels_maria_2008, title={Flexible and lithography-compatible copper foil substrates for ferroelectric thin films}, volume={516}, ISSN={["0040-6090"]}, DOI={10.1016/j.tsf.2007.08.093}, abstractNote={A process has been developed for preparing a low surface roughness copper foil by evaporation and subsequent peel-off of copper metal layers on glass slides. These 15 micron thick substrates exhibited roughness values between 1 and 2 nm root-mean-square (RMS) and 9 nm RMS over 25 μm2 and 100 μm2 analysis areas, respectively. The deposition and crystallization of barium strontium titanate layers were demonstrated on these smoother variant foils. The fully processed dielectric layers exhibited field tunability greater than 5:1, and could withstand fields in excess of 750 kV/cm. High field loss tangents below 0.007 were observed, making these materials excellent candidates for microwave devices. Finally, a process of lamination and contact lithography was used to demonstrate patterning of micron-scale features suitable for microwave circuit element designs.}, number={10}, journal={THIN SOLID FILMS}, author={Laughlin, B. and Ihlefeld, J. F. and Daniels, Patrick and Maria, J. -P.}, year={2008}, month={Mar}, pages={3294–3297} }
 @article{ihlefeld_borland_maria_2008, title={Synthesis and properties of barium titanate stannate thin films by chemical solution deposition}, volume={43}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-008-2618-x}, number={12}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Ihlefeld, Jon F. and Borland, William J. and Maria, Jon-Paul}, year={2008}, month={Jun}, pages={4264–4270} }
 @article{ihlefeld_borland_maria_2007, title={Enhanced Dielectric and Crystalline Properties in Ferroelectric Barium Titanate Thin Films}, volume={17}, ISSN={1616-301X}, url={http://dx.doi.org/10.1002/adfm.200601159}, DOI={10.1002/adfm.200601159}, abstractNote={Abstract}, number={7}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Ihlefeld, J. F. and Borland, W. J. and Maria, J.-P.}, year={2007}, month={Mar}, pages={1199–1203} }
 @article{daniels_ihlefeld_borland_maria_2007, title={Smart electrodes for ultralarge-area thin film capacitors}, volume={22}, ISSN={["0884-2914"]}, DOI={10.1557/JMR.2007.0272}, abstractNote={A process suitable for preparing metal-insulator-metal thin film capacitors with submicron insulating layers and top electrodes with cm-scale dimensions is presented. Most importantly, this process does not require sophisticated deposition equipment or a clean room environment. The key to large area yield is co-firing the insulator film with a non-dewetting electrode during the dielectric crystallization/densification anneal. We propose a mechanism of electrode dewetting during the high temperature anneal where the metal laterally retreats from geometric asperities that compromise the integrity of the insulating layer. This behavior is driven by surface energy minimization, which promotes metal migration away from the regions of high curvature. This methodology is not material specific, and only requires a top electrode with a large contact angle to the dielectric in question. Using this technique, functional thin film capacitors with 2.5 cm lateral dimensions and 1 μm dielectric thicknesses can be routinely prepared.}, number={7}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Daniels, Patrick and Ihlefeld, Jon and Borland, William and Maria, Jon-Paul}, year={2007}, month={Jul}, pages={1763–1766} }
 @article{craft_ihlefeld_losego_collazo_sitar_maria_2006, title={MgO epitaxy on GaN (0002) surfaces by molecular beam epitaxy}, volume={88}, ISSN={["1077-3118"]}, DOI={10.1063/1.2201041}, abstractNote={We report on the epitaxial deposition of magnesium oxide films with [111] crystallographic orientation on (0002) GaN by molecular beam epitaxy. Specifically, we use an adsorption controlled growth mechanism to initiate the growth process. Electron diffraction shows a spotty intense pattern without intensity fluctuations during growth and evidence of in-plane twinning. X-ray diffraction reveals the films to be epitaxial with full width at half maximum values of 0.3°, 0.5°, and 1° in 2θ, ϕ, and χ circles, respectively. Wet etching of the GaN surface with a HCl:HF mixture prior to growth is critical for achieving high crystalline quality. Epitaxial growth is observed between room temperature and 650°C, with negligible changes in crystalline quality with increased temperature. Atomic force microscopy analysis shows grainy surfaces with feature sizes near 10nm and rms roughness values of 1.4Å over 1μm2 areas. X-ray diffraction analysis suggests MgO film stability up to 850°C in ex situ air annealing.}, number={21}, journal={APPLIED PHYSICS LETTERS}, author={Craft, H. S. and Ihlefeld, J. F. and Losego, M. D. and Collazo, R. and Sitar, Z. and Maria, J. -P.}, year={2006}, month={May} }
 @misc{borland_ihlefeld_kingon_maria_2006, title={Thin film dielectrics for capacitors and methods of making thereof}, volume={7,029,971}, number={2006 Apr. 18}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Borland, W. J. and Ihlefeld, J. F. and Kingon, A. I. and Maria, J. P.}, year={2006} }
 @article{ihlefeld_laughlin_hunt-lowery_borland_kingon_maria_2005, title={Copper compatible barium titanate thin films for embedded passives}, volume={14}, ISSN={["1573-8663"]}, DOI={10.1007/s10832-005-0866-6}, number={2}, journal={JOURNAL OF ELECTROCERAMICS}, author={Ihlefeld, J and Laughlin, B and Hunt-Lowery, A and Borland, W and Kingon, A and Maria, JP}, year={2005}, month={Mar}, pages={95–102} }
 @article{ihlefeld_maria_borland_2005, title={Dielectric and microstructural properties of barium titanate zirconate thin films on copper substrates}, volume={20}, ISSN={["2044-5326"]}, DOI={10.1557/JMR.2005.0342}, abstractNote={Barium titanate zirconate, Ba(Ti1−xZrx)O3 (0 ≤ x ≤ 0.25), thin films were deposited via the chemical solution deposition (CSD) method directly on copper foils. The films were processed in a reductive atmosphere containing nitrogen, water vapor, and hydrogen gas at 900 °C to preserve the metallic copper substrate during crystallization. Increasing the fraction of BaZrO3 revealed several effects, including an increase in unit cell dimensions, a decrease in both the temperature and value of the maximum permittivity, as well as a decrease in the average grain size of the films. The decrease in the relative permittivity was attributed to a grain size effect as opposed to zirconium substitution. In film compositions containing 25 mol% BaZrO3, the permittivity below Tmax became dispersive, and the ferroelectric transitions became increasingly diffuse. These characteristics suggest relaxor-like behavior. The dielectric tunability of Ba(Ti1−xZrx)O3 was studied at room temperature and at Tmax for each composition. There was little variation in the tunability with measurement temperature; however compositions that were ferroelectric at room temperature saw a decrease in hysteresis at Tmax, and all compositions showed an increase in permittivity.}, number={10}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Ihlefeld, JF and Maria, JP and Borland, W}, year={2005}, month={Oct}, pages={2838–2844} }
 @article{losego_jimison_ihlefeld_maria_2005, title={Ferroelectric response from lead zirconate titanate thin films prepared directly on low-resistivity copper substrates}, volume={86}, ISSN={["0003-6951"]}, DOI={10.1063/1.1919388}, abstractNote={We demonstrate films of the well-known ferroelectric lead zirconate titanate (PZT) prepared directly on copper foils by chemical solution deposition (CSD). The films exhibit saturating polarization hysteresis, remanent polarization values of 26μC∕cm2, and permittivities of 800; these properties are comparable to those achieved using semiconductor-grade substrates. The preparation methodology is founded upon an understanding of solution chemistry as opposed to conventional gas-phase ∕ condensed-phase equilibrium approaches. By adopting this technique, base-metal compatibility can be achieved using much lower temperatures, and a broader set of devices can be prepared offering intimate contact with high conductivity, easily patternable, or ferromagnetic metals.}, number={17}, journal={APPLIED PHYSICS LETTERS}, author={Losego, MD and Jimison, LH and Ihlefeld, JF and Maria, JP}, year={2005}, month={Apr} }
 @article{laughlin_ihlefeld_maria_2005, title={Preparation of sputtered (Ba-x,Sr1-x)TiO3 thin films directly on copper}, volume={88}, ISSN={["1551-2916"]}, DOI={10.1111/j.1551-2916.2005.00488.x}, abstractNote={ (Ba0.6,Sr0.4)TiO3 (BST) films were deposited on copper foils by radio frequency magnetron sputtering. By the use of controlled pO2 high‐temperature anneals, the films were completely crystallized in the absence of substrate oxidation. X‐ray diffraction and transmission electron microscopy (TEM) revealed an abrupt Cu/BST interface. The deposited BST films exhibit a zero bias permittivity and loss tangent values of 600 and 0.018, respectively. An electrical tunability ratio of 3.5:1 is observed on these metal–insulator–metal devices. Devices show leakage currents of 10−8 A/cm2 at ±10 V/μm, and loss tangents as low as 0.003 in fields approaching 40 V/μm. }, number={9}, journal={JOURNAL OF THE AMERICAN CERAMIC SOCIETY}, author={Laughlin, B and Ihlefeld, J and Maria, JP}, year={2005}, month={Sep}, pages={2652–2654} }