Compositional, structural and electrical characterization of barium titanate thin films prepared on fused silica and Si(111) by spray pyrolysis

Barium titanate thin films have been prepared by chemical spray pyrolysis, Aqueous spray solutions of titanium isopropoxide and barium acetate, equimo lar with respect to titanium and barium, were used as precursors. Depositio n was carried out at a substrate temperature of 250 degrees C, As-deposited films are amorphous. Films of BaTiO3 (perovskite) were obtained by calcina tion in air to 600 degrees C for various hours. Perovskite films are compac t and smooth, according to their morphological aspect studied by scanning e lectron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) combined w ith 4 keV Ar+ depth profiling has shown that the as-deposited film correspo nds to BaTiO3 and that its composition stays constant through the whole fil m thickness. Residual carbon tin the form of BaCO3) coming from the organic precursor solutions is only detected at the surface of the film, limited t o the first atomic monolayers as revealed by depth profiling. Calcination i n air at 600 degrees C decreases this amount but BaCO3 is still present at a percentage of 25% with respect to the whole amount of Ba in the film surf ace. Electrical characterization of a calcined BaTiO3 film deposited on con ductive n-type Si(111) was carried out with impedance spectroscopy in a fre quency range of 10 Hz to 1 MHz. Assuming a film thickness of 100 nm as dedu ced by XPS depth profiling, the relative dielectric permittivity of our fil ms can be estimated to be 80 at a frequency of 1 kHz. Copyright (C) 2000 Jo hn Wiley & Sons, Ltd.