Effect of phase separation on optical and electrical properties of Sn-Sb-Se glassy films

Abstract

This paper reports the effect of phase separation on the structural, optical and electrical properties of thermally evaporated Snx Sb20Se70–x (x = 10, 11, 12.5) films. The X-ray diffraction studies of the devitrified films show the crystallization of SnSe2, Sn2Sb4Se8 and Sn4Sb4Se10 phases for x = 12.5 film, while Sb2Se3 is the other major phase in all the film samples. The optical constants are calculated by using Swanpole's standard envelop method. The dispersion of the refractive index is discussed in terms of the Cauchy's dispersion relation and the Wample–DiDomenico (WDD) single-oscillator model in the weak absorption region. The optical gap and the tailing parameter were calculated in the fundamental absorption region, while the Urbach energy was calculated by using the value of extinction coefficients. The dc conductivity measurements with temperature have also been performed and electrical conduction has been discussed in conjunction with the Meyer–Neldel rule for the present system. These results have been discussed taking into consideration the structural modifications induced by the phase separation in the present system. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)