EXAFS Study of the Local Order in Ge-As-Se Glasses

The nearest-neighbour environment of the Ge, As and Se atoms in ternary GexAsySe1-x-y systems with same mean coordination number (MCN = 2.5) have been investigated by the Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS). For all the glass compositions, Ge, As and Se are always 4, 3 and 2 coordinated, respectively. Ge atoms are bonded to Se atoms exclusively in the compositional range studied. Homopolar bonds are formed between some As or Se atoms in non-stoichiometric glasses. The results suggest a combined effect of chemical ordering and topological in this system.