On the structure of Ge–As–Te–Cu glasses

• Cu binds predominantly to Te in 0.9(Ge0.1As0.15Te0.75)–0.1Cu.
• Cu–Cu and Cu–As bonding is significant in 0.9(Ge0.05As0.55Te0.4)–0.1Cu.
• Ge and As atoms have 4 and 3 Ge/As/Te neighbors in both positions.
• In 0.9(Ge0.1As0.15Te0.75)–0.1Cu the formation of ‘extra’ Te–Te bonds can be observed.

Short range order in glassy 0.9(Ge0.1As0.15Te0.75)–0.1Cu (GATC1) and 0.9(Ge0.05As0.55Te0.4)–0.1Cu (GATC2) was studied by neutron- and X-ray diffraction as well as EXAFS (extended X-ray absorption fine structure) measurements at the K-edges of all components. The reverse Monte Carlo simulation technique was used to create models consistent with all experimental datasets. It was found that Cu binds predominantly to Te in GATC1 while Cu–As and Cu–Cu bonding is also significant in GATC2. Ge and As atoms have 4 and 3 Ge/As/Te neighbors in both compositions. In GATC1 the formation of ‘extra’ Te–Te bonds can be observed, similarly to GeTe4–AgI glasses.