Effect of copper on the local structure of GeSe2Cu probed by Raman spectroscopy

Glassy GeSe2 is known to exhibit photodarkening that is extinguished by the presence of copper. Bulk glasses of GeSe2Cux (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 A1c (218 cm−1) and Ge–Ge (178 cm−1) peaks relative to the A1 (201 cm−1) for compositions of less than x=0.05 copper but changed very little at higher compositions. The position of the A1 and A1c 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(Se1/2)4 chains.