Short range order in Ge-As-Se glasses

The structure of Ge_xAs₁₀Se_90-x (x = 10, 17.5, 22.5, 27.5, 30, 35) glasses as well as some other compositions extensively used in infrared optics, e.g. GASIR® (Ge₂₂As₂₀Se₅₈) and AMTIR-1 (Ge₃₃As₁₂Se₅₅) has been investigated by X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) measurements at the Ge, As and Se K-edges. Structural models have been obtained by fitting simultaneously XRD and EXAFS data by the reverse Monte Carlo simulation technique. Unlike other IV-V-VI glasses (e.g. Ge-As-S, Ge-Sb-Te, Ge-Sb-Se, Ge-As-Te) Ge-As-Se glasses are characterized by the lack of preferential bonding and behave as random covalent networks: Ge-Ge, Ge-As or As-As bonds can be found in Se-rich compositions while Se-Se bonding remains in strongly Se-deficient glasses as well.