Optical and structural properties of (Ba, Sr)TiO3 thin films grown by radio-frequency magnetron sputtering

Abstract

We studied the structural and optical properties of (Ba, Sr)TiO3 (BST) films deposited on the transparent substrates at various temperatures of 350-650 degrees C and annealed at 450-650 degrees C. Improved crystallization can be observed on 650 degrees C annealed film whose substrate temperature is 350 degrees C. The refractive index increased from 2.17 to 2.59 at lambda = 410 nm for the BST films deposited at 350-650 degrees C and it varied from 2.17 to 2.25 after annealing up to 650 degrees C. In addition, the refractive-index dispersion data related to the short-range-order structure of BST films obeyed the single-oscillation energy model. The indirect energy gap of the films deposited on Al2O3 and quartz substrates was found to be about 3.5 eV. According to the analysis of reflectance data, the optical inhomogeneity of films can be reduced by depositing the films at intermediate temperatures 450-550 degrees C. (C) 1999 Kluwer Academic Publishers.