Effect of Change in Ba Concentration on Crystallintiy and Dielectric Constant of the Sol-Gel Deposited Barium Strontium Titante (BST) Films on n-Type Si Wafer

Thin (Bax, Sr1 – x)TiO3 (BST) films of different chemical compositions (x = 0.3 0.5 & 0.7) were prepared by the sol-gel process using barium acetate, strontium acetate and titanium isopropoxide as metal alkoxides. The titanium isopropoxide was dissolved in acetyl acetone (chelating agent) and mixing the resultant solution with barium and strontium acetate dissolved in acetic acid solution. The alkoxide group in titanium isopropoxide was replaced by acetate ligand and after hydrolysis and condensation process a complex solution was obtained. This solution was deposited on n-type (111) Si wafers by spin coating and after drying at 350 oC the samples were annealed at 700 oC in oxygen ambient. The precise control of composition of different species is important for producing good quality films having high crystallinity and dielectric constant. The crystallinity of the film was found to increase with the increase of Ba concentration as found from X-ray diffraction. The calculated value of dielectric constant from CV measurements revealed that the film of (Ba0.7, Sr0.3) TiO3 had the maximum dielectric constant as 463 and the surface was examined by SEM.