Structural investigation of chalcogenide and chalcohalide glasses using Raman spectroscopy

HV- and HH-polarized Raman spectra of the chalcogenide glasses Ge30As10Se(6 0-x)Tex, (25 less than or equal to x less than or equal to 35) and the chal cohalide glasses Ge30As10Se30Te(30-y) I-y (0 less than or equal to y less t han 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-xT ex] mixed tetrahedral units, and Ge-Te-Ge chains. The substitution of iodin e 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 m ain structural units for the chalcohalide glasses are [AsSexTeyIz] mixed py ramidal 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 properti es 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.