Photoacoustic investigation of the optical absorption and thermal diffusivity in Si_xTe_100-x glasses

Abstract

The photoacoustic technique is used to determine the optical energy gap E₀ of bulk Si_xTe_100-x glasses in the glass-forming region 10 ≤ x ≤ 28. The thermal diffusivity a of these samples has also been measured. The variation of E₀ and a with x is reported. It is found that E₀ increases with x nearly linearly with a sharp decrease in the rate of increase beyond x = 20. The thermal diffusivity also increases with x up to x = 20 but decreases for compositions with higher values of x. The observed behaviour is explained on the basis of a chemical bond approach. It is accounted for in terms of the increase in the number of Te-Te bonds and formation of SiTe₄ tetrahedra with an increase in the chalcogen content.