Structural investigation of chalcogenide and chalcohalide glasses using Raman spectroscopy

HV- and HH-polarized Raman spectra of the chalcogenide glasses Ge30As10Se(60-x)Tex, (25 less than or equal to x less than or equal to 35) and the chalcohalide glasses Ge30As10Se30Te(30-y) I-y (0 less than or equal to y less than or equal to 30), Ge30As10Se35Te(25-z)Iz (0 less than or equal to z less than or equal to 20) were investigated. For the chalcogenide glasses, the main structural units include [AsSe3-xTex] mixed pyramidal units, [GeSe4-xTex] mixed tetrahedral units, and Ge-Te-Ge chains. The substitution of iodine for tellurium in the chalcohalide glasses results in the formation of Ge-I, As-I, and Se-I bonds which break up the three-dimensional network. The main structural units for the chalcohalide glasses are [AsSexTeyIz] mixed pyramidal units where x+y+z = 3, [GeSexTey I-z] mixed tetrahedral units where x + y + z = 4, and GeSe3/2I mixed tetrahedral units. The symmetry properties of these structural units has been determined through the dependence of the depolarization ratio on the frequency shift. (C) 1999 Elsevier Science B.V. All rights reserved.