Electrical and optical properties of Sb31Se36Ag33

The electrical conductivity and the optical absorption of vacuum-evaporated Sb,,Se,,Ag,, amorphous thin films with thicknesses in the range (115.495-1 80.1 nm) were studied. The thermal conductivity of the investigated composi tion has also been studied. It was found experimentally that the conduction in all the samples takes place via thermally activated tunnelling in the e ntire range of temperature (318-353 K). In the high-temperature region (353 -373 K) below the corresponding glass transition temperature T-g (T-g congr uent to 410 K) the conduction mechanism remains the same with a higher acti vation energy Delta E, while at lower temperature (298-318 K), the conducti on is due to variable range hopping in the localized states near Fermi leve l. An increase in the film thickness was found to result in the increase of the room temperature electrical conductivity sigma(RT) (300 R), decrease i n the activation energy Delta E and the pre-exponential factor a, for the c onsidered composition. The coefficient of thermal conductivity psi increase s linearly with temperature for the investigated composition. The optical a bsorption showed that the absorption edge moves to a higher wavelength as t he thickness of the films are increased, and the optical absorption is due to two transitions. The optical band gap E-opt was found to be increasing w ith the increase in film thickness. (C) 2000 Elsevier Science Ltd. All righ ts reserved.