Electrical properties of the perovskite (Pb, La)TiO3 films deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition

Abstract

The effects of La content and rapid thermal annealing (RTA) on the capacitance (C-V) and leakage current (J-E) properties of the PLT films were investigated. The films were deposited on Pt/Ti/SiO2/Si substrates at 480 degrees C by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD). The La doped films showed slim P-E hysteresis curves and almost no frequency dependency of permittivity. As the La content increased beyond 11%, Pb was excessively incorporated into the PLT film, resulting in nonstoichiometric compositions with (Pb + La)/Ti > 1, degraded crystallinity and decreased capacitance. After RTA at 700 degrees C, C-V curves became symmetric and leakage current characteristics were improved, but the crystallinity a nd the ferroelectricity of the films were not so much improved although the film became stoichiometric. The leakage current of the films was controlled by Schottky conduction except for the low electric field region where the trap current of mobile charges or hopping conduction appeared to be dominant. In order to explain the RTA dependence of the C-V shift and the polarity dependence of the J-E characteristics of the PLT films, a physical model was suggested, based on the surface states and Pb vacancies, which affects the width of the space charge region and the height of the Schottky barrier. (C) 1998 Kluwer Academic Publishers.