Chemical Solution Deposition of PLZT Films on Base Metal Foils
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Chemical Solution Deposition of PLZT Films on Base Metal Foils D.-J. Kim1, D. Y. Kaufman2, S. K. Streiffer1, T. H. Lee2, R. Erck2 and O. Auciello1 1
Materials Science Division, Argonne National Laboratory, Argonne, IL Energy Technology Division, Argonne National Laboratory, Argonne, IL
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ABSTRACT In an effort to develop cost effective, volumetrically efficient, high charge density and high energy density capacitors, Pb(Zr,Ti)O3 and La-doped Pb(Zr,Ti)O3 films were deposited by chemical solution deposition on nickel and alloy foils. PZT films deposited on bare foils exhibited lower permittivity and more electric field hysteresis compared to films deposited on platinized silicon substrates, due to the formation of low capacitance interfacial layers and/or diffusion of foil elements into the PZT. However, an ultimate dielectric breakdown strength of approximately 1.35 MV/cm was obtained for a film thickness of 1.8 µm, corresponding to a withstand voltage of 245 V. A reduced temperature dependence of capacitance was observed with decreasing film thickness. In order to improve the dielectric response, barrier layers of LaNiO3, Ru, or Ir were deposited on top of the metal foils used as substrates. The barrier improved relative permittivity and reduced hysteresis in relative permittivity as a function of dc bias. INTRODUCTION While significant progress has been made in circuit and module design with respect to active component, substantial advances are still required for passive components, including capacitors. Specific improvements desired for capacitor technology include higher capacitance density, higher dielectric breakdown strength, decreased electrical and thermal losses, improved reliability, and lower-cost electrode materials. One attractive approach to achieve these enhancements is to utilize thin film capacitor devices employing ferroelectric materials. Thin film dielectric layers can exhibit improved materials uniformity, higher density, and smoother electrode-dielectric interfaces, all of which will lead to higher breakdown strength. Additionally, the extremely fine microstructure typical of thin films, coupled with mechanical clamping of the dielectric thin film by the substrate, can result in improved temperature stability. Thin film technologies can also reduce the device footprints and permit the integration directly onto the circuitry. By replacing relatively expensive noble metal electrodes with base metal or alloy foils, insertion into a broad range of cost sensitive applications becomes possible. Recently, several groups have explored this approach, demonstrating its potentials [1-5]. In this study, we have used chemical solution deposition (CSD) to synthesize Pb(Zr0.52,Ti0.48)O3 (PZT) and 8% La-doped Pb(Zr0.52,Ti0.48)O3 (PLZT) films on nickel and alloy foils, as part of an effort to address the technology issues described above. The impacts on dielectric performance of film thickness, La-doping, and insertion of barrier layers at the dielectric/foil interface were examined in order to optim
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