Pressure induced structural change of clusters in chalcogenide glasses

It is found that the intensity of the companion A₁ band (A^c₁) relative to that of the A₁ band decreases with increasing pressure in g‐Ge_1−xSe_x. In g‐GeSe₂, a simple extrapolation of the intensity ratio gives a vanishing of the A^c₁ band at 48 kbar. The effect is related to a morphological transition for lack of a quasi‐planar correlation at high pressures. In sulfur rich glasses, the three characteristic modes, 153, 219 and 475 cm⁻¹, of the S₈ ring disappear at 20–27 kbar, depending upon x and the laser light intensity. It is suggested that sulfur chains in g‐Ge_1−xS_x are like broken S₈ rings in contrast with selenium chains in g‐Ge_1−xSe_x having long spatial extent. We have observed a softening of the SnS₄‐A₁ mode at high pressures in g‐Ge_0.6Sn_0.4S₃ where the tin atoms are not incorporated into sulfur clusters but into the GeS_4/2 clusters. The glass forming tendency of the (Ge,Sn) chalcogenide glass system is discussed, based on our high pressure works and in relation to a significant composition x=0.8.