Compositional and Structural Properties of Sputtered Plzt Thin Films

Abstract

AbstractThin films of lanthanum-modified lead zirconate-titanate (PLZT) were prepared by rf magnetron sputtering from a single oxide target onto a heated substrate. The target consisted of Pbl-xLaxZryTi1-yO3 with composition close to x=8% and y= 65%, either as a loose powder or a solid sintered disk. Under appropriate conditions, the desired perovskite phase formed in situ without any subsequent post-anneal. Film composition and structure were correlated with deposition parameters, including substrate temperature, target composition, gas pressures, and target aging. For deposition onto MgO or A12O3 crystalline substrates, perovskite PLZT films formed if there was sufficient Pb at the target surface, sufficient oxygen in the sputter gas (≈ 50%), and a substrate temperature >≈600°C. Target heating led to excessive Pb loss from the loose powder target; this was much less significant for the solid target. In addition, it was found that deposition onto an epitaxial perovskite substrate promoted formation of the perovskite phase, leading to an epitaxial film. A prototype ferroelectric capacitor was fabricated by depositing a conducting perovskite film (the high-Tc superconductor YBa2 Cu3O7 ) on a perovskite substrate, sputtering PLZT on top, with Ag for a top electrode. Measurements indicate a remanent polarization of 5 μC/cm2 and a coercive field of 900 V/cm.