Effect of copper on the local structure of GeSe 2Cu x probed by Raman spectroscopy

Abstract

Glassy GeSe 2 is known to exhibit photodarkening that is extinguished by the presence of copper. Bulk glasses of GeSe 2Cu x (0< x<0.16), prepared by melt-quenching, were studied by Raman spectroscopy to ascertain the effect of copper on the local structure of the glass. Decreases were observed in relative areas of the A 1c (218 cm −1) and Ge–Ge (178 cm −1) peaks relative to the A 1 (201 cm −1) for compositions of less than x=0.05 copper but changed very little at higher compositions. The position of the A 1 and A 1c peaks decreased by 2 cm −1 in low copper compositions. The density of the samples also increased sharply below x=0.05 and more gradually above x=0.05. The copper is seen as affecting the defects (Ge–Ge bonds) in the stoichiometric germanium–selenium glass but not affecting the tetrahedral Ge(Se 1/2) 4 chains.