EFFECT OF COMPOSITION, FILM THICKNESS AND ANNEALING ON THE OPTICAL-PROPERTIES OF BI-SB-SE THIN-FILMS

Thin films of Bi10SbxSe90-x (x greater than or equal to 35, 40, 45) of different composition and thickness, were deposited on glass substrat es by vacuum evaporation. Optical absorption measurements show that th e fundamental absorption edge is a function of glass composition, film thickness and annealing temperature. The optical absorption is due to indirect electronic transitions. The value of the optical band gap wa s found to increase with thickness and decreasing the antimony content and with increasing temperature of heat treatment. The validity of th e Urbach rule was investigated and the respective parameters estimated . X-ray diffraction was used to obtain an insight into the structural information.