Microstructure dependence of electrical properties of (Ba0.5Sr0.5)TiO3 thin films deposited on Pt/SiO2/Si

Stoichiometric (Ba0.5Sr0.5S)TiO3 (BST) thin films with various thicknesses have been prepared on Pt/SiO2/Si substrates using conventional rf magnetron sputtering method with a ceramic target containing excess BaO and SrO. With increasing film thickness, the grain size of the BST films gradually increased. It was observed that the dielectric constant increased from 348 to 758 when grain size increased from 32 to 82 nm in BST films deposited at 600 degrees C. The decrease of dielectric constant in thinner BST films was attributed to the initial low dielectric constant layer and small grain size. In the current-voltage curves for BST films, higher leakage current densities and narrower flat regions (hopping conduction region) in the low bias field were obtained with increasing grain size. (C) 1996 American Institute of Physics.