On the microstructure and optical properties of Ba0.5Sr0.5TiO3 films

Abstract

Thin films of Ba1-xSrxTiO3 (x = 0.5) were prepared on the (<1(1)over bar 02>) plane of sapphire substrates by pulsed laser deposition. Crystallographic studies show that the films are polycrystalline with a strong reflection from the (111) plane. Scanning electron micrographs reveal smooth surfaces. The index of refraction and the absorption coefficient were determined at room temperature in the wavelength range 382-800 nm from spectrophotometer measurements of the transmittance at normal incidence using the method devised by Swanepoel. The average value of the refractive index is found to be 2.06 in the visible spectrum; the higher values near the UV are associated with the fundamental band gap absorption. The dispersion of the refractive index is interpreted in terms of a single electronic oscillator at 7.16 eV. The direct band gap energy is found to be 3.96 eV. (C) 1997 Elsevier Science S.A.