Chemical solution deposition of ferroelectric lead lanthanum zirconate titanate films on base-metal foils

Abstract

Development of electronic devices with better performance and smaller size requires the passive components to be embedded within a printed wire board (PWB). The “film-on-foil” approach is the most viable method for embedding these components within a PWB. We have deposited high-permittivity ferroelectric lead lanthanum zirconate titanate (Pb0.92La0.08Zr0.52Ti0.48Ox, PLZT 8/52/48) films on base metal foils by chemical solution deposition. These prefabricated capacitor sheets can be embedded into PWBs for power electronic applications. To eliminate the parasitic effect caused by the formation of a low-permittivity interfacial oxide, a conductive buffer layer of lanthanum nickel oxide (LNO) was applied by chemical solution deposition on nickel foil before the deposition of PLZT. With a ≈0.7-μm-thick ferroelectric PLZT film grown on LNO-buffered nickel foil, we measured capacitance densities of 1.5 μF/cm2, breakdown field strength Eb >1.2 MV/cm, and leakage current density of 2 × 10–8A/cm2. The dielectric relaxation current decay obeys the Curie-von Schweidler law, with exponent n = 0.85 and 0.94 for PLZT grown directly on Ni and that grown on LNO-buffered Ni foils, respectively. When compared with samples deposited directly on Ni substrate, PLZT grown on LNO buffered Ni substrates exhibit slimmer hysteresis loop and better energy storage capability. With these desirable characters, PLZT film-on-foil capacitors hold particular promise for use in high-voltage embedded passives.