Effect of (La0.5Sr0.5)CoO3 and Pt intermediate layers on improving the stability of Pb1–xLaxTi1–x/4O3 films

Abstract

Deposition of a (La0.5Sr0.5)CoO3 (LSCO) layer on top of Pt/Ti/Si substrates was observed to substantially improve the stability of the subsequently deposited Pb1−xLaxTi1−x/4O3 (PLT) films. Platinum coating of silicon substrates by itself is known to enhance the formation of PLT phase. In this paper, the elemental depth profile examined by secondary ion mass spectroscopy (SIMS) and the structural profile examined by grazing angle incident x-ray diffractometry (GIXD) reveals that the Ti species precoated underneath the Pt layer diffuses outward through the Pt layer at high temperature, forming a rutile TiO2 layer on top of Pt coating. It is this outermost TiO2 layer which promotes the transformation kinetics of the PLT species adhered onto substrates into the perovskite phase. Thus obtained films (PLT/Pt/Ti/Si) are, however, not stable enough to survive subsequent high-temperature processing. On the other hand, the PLT/LSCO/Pt/Ti/Si films, which incorporate LSCO as buffer layer, can survive 650 °C without significant deterioration.