Optical investigation of a-Se 100 x Bi x alloys

The optical properties of a-Se100� xBix thin films (where x ¼ 0:0, 0.5, 2.5, and 5) have been studied in the wavelength range 540–900 nm. It was found that the optical band gap decreases on increasing Bi concentration in the a-Se100� xBix system. The value of refractive index n decreases, while the value of the extinction coefficient k increases with increasing photon energy. The dc conductivity measurement of a-Se100� xBix thin films has been reported in the temperature range 349–375 K. It has been observed that the activation energy decreases with increasing Bi concentration. 2002 Elsevier Science B.V. All rights reserved.