The Cu and Te coordination environments in Cu-doped Ge–Te glasses

The structure of Ge20Te80, Ge15Cu8Te77 and Ge15Cu5Te80 glasses was investigated by diffraction techniques and extended X-ray absorption fine structure measurements. Large structural models were generated by fitting experimental data by the reverse Monte Carlo simulation technique. In Ge20Te80 glass, both Ge and Te obey the 8 − N rule, and the structure is built up of GeTe4 tetrahedra connected via Te–Te bonding or shared Te atoms connected to two Ge atoms. The coordination number of Te is significantly higher than 2 in Ge15Cu8Te77. The average coordination number of Cu is 3.41 ± 1 in this alloy. In Ge15Cu5Te80 glass, Cu binds mostly to Te, while Cu–Cu bonding is significant in Ge15Cu8Te77.