Short range order in Ge-As-Se glasses

Abstract

The structure of GexAs10Se90x (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.