Abstract
The total structure factor, S(K), have been obtained for the chalcogenide Ge20Se80-xTex (where x = 0, 10, 20, and 30 at. %) glasses using x-ray diffraction in the wave vector interval 0.28 <= K <= 6.87 angstrom(-1). The appearance of the first sharp diffraction peak in the structure factor indicates the presence of the intermediate range order. The radii of the first-and second-coordination shells (r(1), r(2)) are increased linearly with Te addition. The large covalent radius of Te atom in compare with that of Se atom was behind the above linear increase. The first coordination number shows insignificant changes with Te content. The obtained values of r(1)/r(2) ratio and the corresponding bond angle (Theta) indicate that the structural units inside the present alloys are Ge(Se-1/2)(4) tetrahedra connected by chains of the chalcogen atoms. Raman spectra confirm the above conclusion and in the same time exclude the existence of Ge(Te-1/2)(4) tetrahedra. Based on the chemical ordered network mode, Te-Te bonds are responsible for the different behavior of Te-rich (30 at. %) glass from others. (C) 2010 American Institute of Physics. [doi:10.1063/1.3488907]