Effects of Excess Pb and Substrate on Crystallization Processes of Amorphous Pb(Zr, Ti)O₃ Thin Films Prepared by RF Magnetron Sputtering

Abstract

Effects of excess Pb and substrate on the crystallization processes of amorphous lead-zirconate-titanate (a-PZT) thin films by post-annealing in oxygen ambient were investigated to lower the crystallization temperature of the films with a single perovskite phase. A-PZT films were prepared on Ir and Pt substrates with a 2-nm-thick Ti buffer layer on their surfaces, and on a SrRuO 3 substrate by cosputtering Pb(Zr 0.5 Ti 0.5 )O 3 and PbO targets. Analyses by in situ heating X-ray diffraction revealed that the crystallization processes strongly depend on the amount of excess Pb contained in the as-prepared a-PZT and substrates. By controlling the rf power supplied to the PbO target during the deposition, we obtained single perovskite phase PZT films at 480° C, 520° C and 580° C on SrRuO 3 , Ir and Pt substrates, respectively. The crystallized PZT films exhibited excellent ferroelectric properties. For the 150-nm-thick PZT film, crystallized by rapid thermal annealing at 600° C for 20 s, we obtained a coercive field of 40 kV/cm (0.6 V), a remanent polarization density of 15 µ C/cm 2 and polarization switching endurance over 1×10 9 cycles with Ir top and bottom electrodes.