@article{losego_paisley_craft_lam_sachet_mita_collazo_sitar_maria_2016, title={Selective area epitaxy of magnesium oxide thin films on gallium nitride surfaces}, volume={31}, ISSN={["2044-5326"]}, DOI={10.1557/jmr.2015.332}, abstractNote={Abstract}, number={1}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Losego, Mark D. and Paisley, Elizabeth A. and Craft, H. Spalding and Lam, Peter G. and Sachet, Edward and Mita, Seiji and Collazo, Ramon and Sitar, Zlatko and Maria, Jon-Paul}, year={2016}, month={Jan}, pages={36–45} }
 @article{garten_lam_harris_maria_trolier-mckinstry_2014, title={Residual ferroelectricity in barium strontium titanate thin film tunable dielectrics}, volume={116}, DOI={10.1063/1.4891717}, abstractNote={Loss reduction is critical to develop Ba1−xSrxTiO3 thin film tunable microwave dielectric components and dielectric energy storage devices. The presence of ferroelectricity, and hence the domain wall contributions to dielectric loss, will degrade the tunable performance in the microwave region. In this work, residual ferroelectricity—a persistent ferroelectric response above the global phase transition temperature—was characterized in tunable dielectrics using Rayleigh analysis. Chemical solution deposited Ba0.7Sr0.3TiO3 films, with relative tunabilities of 86% over 250 kV/cm at 100 kHz, demonstrated residual ferroelectricity 65 °C above the ostensible paraelectric transition temperature. Frequency dispersion observed in the dielectric temperature response was consistent with the presence of nanopolar regions as one source of residual ferroelectricity. The application of AC electric field for the Rayleigh analysis of these samples led to a doubling of the dielectric loss for fields over 10 kV/cm at room temperature.}, number={4}, journal={Journal of Applied Physics}, author={Garten, L. M. and Lam, P. and Harris, D. and Maria, J. P. and Trolier-McKinstry, S.}, year={2014} }
 @article{harris_lam_burch_li_rogers_dickey_maria_2014, title={Ultra-high tunability in polycrystalline Ba1−xSrxTiO3 thin films}, volume={105}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4893615}, DOI={10.1063/1.4893615}, abstractNote={Ba0.7Sr0.3TiO3 thin polycrystalline films with an ultra-high capacitance tunability approaching 5:1 at 175 kV/cm were made possible by a flux-assisted synthesis approach. In this process, a small volume fraction of a low melting temperature glass is added during low-temperature sputter deposition. Subsequent annealing activates the liquid phase, which in turn provides the mass transport needed to approach full density, to increase grain size, and to improve crystallinity, and, in so doing, achieves a stronger non-linear dielectric response. Ba0.7Sr0.3TiO3 films with 0%, 1%, 4%, and 7% BaO-3B2O3 flux exhibited grain sizes of 25 nm, 28 nm, 48 nm, and 56 nm, and dielectric tunabilities of 25%, 33%, 64%, and 80% respectively. These values represent substantial improvements when compared to conventionally processed tunable dielectric films.}, number={7}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Harris, D. T. and Lam, P. G. and Burch, M. J. and Li, J. and Rogers, B. J. and Dickey, E. C. and Maria, J.-P.}, year={2014}, month={Aug}, pages={072904} }
 @article{harris_burch_ihlefeld_lam_li_dickey_maria_2013, title={Realizing strain enhanced dielectric properties in BaTiO3 films by liquid phase assisted growth}, volume={103}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4813270}, DOI={10.1063/1.4813270}, abstractNote={The addition of a liquid-forming flux to barium titanate thin films promotes densification and grain growth, improves nonlinear dielectric properties, and allows residual strain to be sustained in polycrystalline films without cracking at thicknesses relevant to device fabrication. Relative tuning, an excellent indicator of crystalline quality and an important material property for tunable microwave devices, increases from 20% to 70%. Films exhibit 0.15% residual differential thermal expansion mismatch strain, resulting in a shift to the paraelectric-ferroelectric phase transition of 50 °C. This result is in excellent agreement with theory, demonstrating the ability to tune ferroic transitions without epitaxial approaches.}, number={1}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Harris, David T. and Burch, Matthew J. and Ihlefeld, Jon F. and Lam, Peter G. and Li, Jing and Dickey, Elizabeth C. and Maria, Jon-Paul}, year={2013}, month={Jul}, pages={012904} }
 @article{shelton_kotula_brennecka_lam_meyer_maria_gibbons_ihlefeld_2012, title={Chemically Homogeneous Complex Oxide Thin Films Via Improved Substrate Metallization}, volume={22}, ISSN={["1616-301X"]}, DOI={10.1002/adfm.201103077}, abstractNote={Abstract}, number={11}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Shelton, Christopher T. and Kotula, Paul G. and Brennecka, Geoff L. and Lam, Peter G. and Meyer, Kelsey E. and Maria, Jon-Paul and Gibbons, Brady J. and Ihlefeld, Jon F.}, year={2012}, month={Jun}, pages={2295–2302} }
 @article{lam_haridasan_feng_steer_kingon_maria_2012, title={Scaling Issues in Ferroelectric Barium Strontium Titanate Tunable Planar Capacitors}, volume={59}, ISSN={["1525-8955"]}, DOI={10.1109/tuffc.2012.2179}, abstractNote={We report on the geometric limits associated with tunability of interdigitated capacitors, specifically regarding the impact of a parasitic non-tunable component that necessarily accompanies a ferroelectric surface capacitor, and can dominate the voltage-dependent response as capacitor dimensions are reduced to achieve the small capacitance values required for impedance matching in the X band. We present a case study of simple gap capacitors prepared and characterized as a function of gap width (i.e., the distance between electrodes) and gap length (i.e., the edge-to-edge gap distance). Our series of measurements reveals that for gap widths in the micrometer range, as gap lengths are reduced to meet sub-picofarad capacitance values, the non-tunable parasitic elements limit the effective tunability. These experimental measurements are supported by a companion set of microwave models that clarify the existence of parallel parasitic elements.}, number={2}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, author={Lam, Peter G. and Haridasan, Vrinda and Feng, Zhiping and Steer, Michael B. and Kingon, Angus I. and Maria, Jon-Paul}, year={2012}, month={Feb}, pages={198–204} }
 @article{wilkerson_lam_gard_steer_2011, title={Distributed Passive Intermodulation Distortion on Transmission Lines}, volume={59}, ISSN={["1557-9670"]}, DOI={10.1109/tmtt.2011.2106138}, abstractNote={A theoretical treatment of distributed electro-thermally induced intermodulation distortion is developed for microstrip transmission lines. The growth of passive intermodulation distortion (PIM) along the length of a line is derived accounting for both loss and electrical dispersion. PIM dependencies on width, length, thickness, and substrate parameters are analyzed leading to design guidelines for low distortion lines. Single metal silver transmission lines are fabricated on sapphire and fused-quartz substrates to isolate the electro-thermal effect and validate the model. Electro-thermal PIM is measured in a two-tone test with tone separation ranging from 4 Hz to 10 kHz.}, number={5}, journal={IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES}, author={Wilkerson, Jonathan R. and Lam, Peter G. and Gard, Kevin G. and Steer, Michael B.}, year={2011}, month={May}, pages={1190–1205} }
 @article{akyildiz_casper_ayguen_lam_maria_2011, title={Hydrothermal BaTiO3 thin films from nanostructured Ti templates}, volume={26}, ISSN={["0884-2914"]}, DOI={10.1557/jmr.2010.102}, abstractNote={Abstract}, number={4}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Akyildiz, Hasan and Casper, Michelle D. and Ayguen, Seymen M. and Lam, Peter G. and Maria, Jon P.}, year={2011}, month={Feb}, pages={592–599} }
 @article{haridasan_lam_feng_fathelbab_maria_kingon_steer_2011, title={Tunable ferroelectric microwave bandpass filters optimised for system-level integration}, volume={5}, ISSN={["1751-8733"]}, DOI={10.1049/iet-map.2010.0461}, abstractNote={Tunable bandpass filters are critical components in emerging radio frequency front-ends. A system-aware design guideline and figure of merit (FOM) are developed for optimum system-level performance. The optimisation metric discussed here deviates from earlier guidelines as the filter bandwidth is allowed to vary in the tunable range, constrained only by the downstream system analogue to digital converter. The system-aware FOM uses worst-case filter design parameters and a tuning sensitivity term that captures the frequency tunability relative to material tunability. A 6.74-8.23-GHz tunable barium strontium titanate-based filter is presented as an example to illustrate the design methodology.}, number={10}, journal={IET MICROWAVES ANTENNAS & PROPAGATION}, author={Haridasan, V. and Lam, P. G. and Feng, Z. and Fathelbab, W. M. and Maria, J-P. and Kingon, A. I. and Steer, M. B.}, year={2011}, month={Jul}, pages={1234–1241} }
 @article{lam_feng_haridasan_kingon_steer_maria_2009, title={The Impact of Metallization Thickness and Geometry for X-Band Tunable Microwave Filters}, volume={56}, ISSN={["1525-8955"]}, DOI={10.1109/TUFFC.2009.1122}, abstractNote={The impact of dc resistance on the performance of X-band filters with ferroelectric varactors was investigated. Two series of combline bandpass filters with specific geometries to isolate sources of conductor losses were designed and synthesized. Combining the changes in filter geometry with microwave measurements and planar filter solver (Sonnet software) simulations quantitatively identified the dependency of insertion loss on overall metallization thickness and local regions of thin metallization. The optimized 8-GHz bandpass filters exhibited insertion losses of 6.8 dB. These filters required 2.5 ¿m of metal thickness (or 3 effective skin depths) to achieve this loss. The trend of loss with thickness indicates diminishing return with additional metal. The integration scheme requires thin regions of metal in the immediate vicinity of the varactors. It is shown through experiment and simulation that short distances (i.e., 15 ¿m) of thin metallization can be tolerated provided that they are located in regions where the resonant microwave current is low.}, number={5}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, author={Lam, Peter G. and Feng, Zhiping and Haridasan, Vrinda and Kingon, Angus I. and Steer, Michael B. and Maria, Jon-Paul}, year={2009}, month={May}, pages={906–911} }
 @article{wang_wang_frankowski_lam_welch_winnik_hartmann_manners_spontak_2007, title={Growth and crystallization of metal-containing block copolymer nanotubes in a selective solvent}, volume={19}, ISSN={["1521-4095"]}, DOI={10.1002/adma.200602230}, abstractNote={Due to their inherent ability to microphase-segregate into well-defined nanostructures, AB diblock copolymers serve as model surfactants to probe complex phase behavior [1] and precursor materials to nanoscale-templated motifs. [2] ^ In the melt, alone or in miscible blends with other (co)polymers, [3] AB molecules can spontaneously self-organize into a variety of nanoscale morphologies, the size and shape of which reflect the packing of A and B repeat units along the interface sepa-rating A-and B-rich spatial regions. Interfacial chain packing and, hence, curvature are strongly dictated by factors such as the size, number and incompatibility of the A and B repeat units along the copolymer backbone. [4] Most block copolymer morphologies of fundamental and technological interest [5] are periodic and are generally classified as either classic or complex, [6] depending on topological metrics such as symmetry, coordination and genus. [7] Aperiodic copolymer melt morphologies described as sponges [8,9] or bicontinuous emulsions [10] are also of contemporary interest. This wealth of block copolymer phase behavior is preserved when copolymer molecules microphase-separate in the presence of one or two selective solvents. [11] In addition to those copolymer nano-structures observed in the melt, however, novel solvated supramolecular aggregates (e.g., crew-cut micelles, [12] nano-tubes, [13] “hamburger” micelles, [14] polymersomes [15] and toroids) [16–18] and network nanostructures [19] likewise develop under favorable conditions. Solvated}, number={17}, journal={ADVANCED MATERIALS}, author={Wang, Xiaosong and Wang, Hai and Frankowski, David J. and Lam, Peter G. and Welch, Paul M. and Winnik, Mitchell A. and Hartmann, Juergen and Manners, Ian and Spontak, Richard J.}, year={2007}, month={Sep}, pages={2279-+} }
 @article{nath_fathelbab_lam_ghosh_aygun_gard_maria_kingon_steer_2006, title={Discrete Barium Strontium Titanate (BST) thin-film interdigital varactors on alumina: Design, fabrication, characterization, and applications}, ISBN={["978-0-7803-9541-1"]}, ISSN={["2576-7216"]}, DOI={10.1109/mwsym.2006.249652}, abstractNote={Discrete barium strontium titanate (BST) thin-film capacitors in industry standard 0603 footprint are introduced and characterized. BST capacitors have a voltage-dependent permittivity, enabling BST thin-film capacitors to be used as tuning elements in frequency agile devices. The capacitance changed by 1.5:1 at 35 V (116 kV/cm) bias. The temperature dependence of the capacitance was measured to be less than plusmn 20 % from -100 degC to +100 degC. A 2nd-order tunable combline bandpass filter on FR4 substrate has been implemented using the discrete BST varactors. The filter showed a center frequency tuning of 22% from 2.14 GHz to 2.61 GHz upon application of 130 V (433 kV/cm) bias. The zero-bias insertion loss was 4.9 dB which decreased to 2.9 dB at the high bias state. The return loss was better than 11 dB over the tuning range. Nonlinear characterization of the filter using two-tone test and a digitally-modulated CDMA 2000 signal showed an IP3 of +32 dBm and an ACPR of better than -50 dBc up to 26 dBm of input power, respectively}, journal={2006 IEEE MTT-S INTERNATIONAL MICROWAVE SYMPOSIUM DIGEST, VOLS 1-5}, author={Nath, Jayesh and Fathelbab, Wael M. and Lam, Peter G. and Ghosh, Dipankar and Aygun, Seymen and Gard, Kevin G. and Maria, J. -P. and Kingon, Angus I. and Steer, Michael B.}, year={2006}, pages={552–555} }
 @article{wei_lam_braunfeld_agard_genzer_spontak_2006, title={Tunable instability mechanisms of polymer thin films by molecular self-assembly}, volume={22}, ISSN={["0743-7463"]}, DOI={10.1021/la061391j}, abstractNote={Incorporation of a block copolymer into a thin polymer film is observed to alter both the rate and mechanism by which the film dewets from an immiscible polymer substrate. Films with little or no copolymer dewet by classical nucleation and growth of circular holes, and the dewetting rate decreases with increasing copolymer concentration. Increasing the copolymer content at constant film thickness generates copolymer micelles that adsorb/aggregate along the polymer/polymer interface and promote nonclassical dewetting fluctuations similar in appearance to spinodal dewetting. At higher copolymer concentrations, dewetting proceeds after a lengthy induction period by the nucleation and growth of flower-shaped holes suggestive of film pinning or viscous fingering. Atomic force microscopy of the polymer/polymer interface after removal of the top film by selective dissolution reveals substantial structural development due to copolymer self-assembly.}, number={21}, journal={LANGMUIR}, author={Wei, Bin and Lam, Peter G. and Braunfeld, Michael B. and Agard, David A. and Genzer, Jan and Spontak, Richard J.}, year={2006}, month={Oct}, pages={8642–8645} }
 @inproceedings{feng_fathelbab_lam_haridasan_maria_kingon_steer, title={A 6.2-7.5 GHz tunable bandpass filter with integrated barium strontium titanate (BST) interdigitated varactors utilizing silver/copper metallization}, booktitle={Rws: 2009 ieee radio and wireless symposium}, author={Feng, Z. P. and Fathelbab, W. M. and Lam, P. G. and Haridasan, V. and Maria, J. and Kingon, A. I. and Steer, M. B.}, pages={607–610} }