Comparative study of amorphous and crystalline (Ba, Sr)Tio₃ thin films deposited by laser ablation

(Ba_0.5.Sr_0.5)TiO₃ thin films (200-300 nm) were deposited on Pt-coated Si substrates by laser ablation at 500 and 650A°C. The leakage currents of crystalline films grown at 650A°C were found to be higher than those of amorphous films grown at 500 A°C. The crystalline thin films showed higher surface roughness than the amorphous films as measured by atomic force microscopy (AFM). A columnar grain structure was observed for crystalline films with a grain size of 20-30 nm by transmission electron microscope (TEM) analysis. These factors may be responsible for high leakage currents of crystalline films. Constant current injection measurements for Au/(Ba_0.5Sr_0.5)TiO₃/Pt capacitors showed that electron trapping states near the top electrode interface were higher in number than at bottom electrode interface. This may be due to the presence of reactive sites on the surface of deposited films as observed by X-ray photoelectron spectroscopy (XPS) measurements.