Precursor dependent properties of Ba/sub 1-x/Sr/sub x/TiO/sub 3/ thin films fabricated by sol-gel method

Abstract

Thin films of barium strontium titanate, Ba/sub 1-x/Sr/sub x/TiO/sub 3/, were deposited on Si and ITO/glass substrates with 200/spl sim/300 nm thickness by sol-gel method. The precursor solution of BST was prepared by mixing the 0.2 M precursor solutions of BaTiO/sub 3/ and SrTiO/sub 3/ with proper molar ratio. The X-ray diffraction (XRD) patterns show characteristic peaks with weak and broad features indicating that the polycrystalline BST film has poor crystallinity. The grain size and the surface morphology of the films were investigated by atomic force microscope (AFM). Especially, dependence of the film structures on the treatments of precursor solution such as hydrolysis and modification with acetic acid was investigated. The I-V (current-voltage) characteristics of the films was also dependent on the precursor structure. The C-V (capacitance-voltage) behavior of the films with MIS (metal-insulator-semiconductor) and MIM (metal-insulator-metal) structures were studied. Also, dielectric permittivity which was very strongly dependent on the crystallinity of the films was discussed in conjunction with precursor structures.