Radial distribution studies of glassy tellurium-silicon alloys

Abstract

X-ray investigations of glassy tellurium-silicon alloys (Si content 10–40 at%) are described. Alloys with 13 to 27 at% Si were obtained in bulk form, non-crystalline samples with 10, 30, 33, 36 and 40 at% Si were obtained by rapid quenching from the melt by the splat-cooling technique. The interference functions and the radial distribution functions of all alloys show a great similarity. However, the positions of the maxima of the pair distribution function decrease continuously with growing Si content and lead to values which are similar to atomic distances in crystalline Te and Si 2Te 3. The areas of the first two peaks of the RDF, F 1 (rougnly 2) and F 2 (roughly 12), are compared with calculated areas derived from different structural models which are based on the short-range order in crystalline Te with a chain structure and in Si 2Te 3 with a tetrahedron configuration. An interstitial model with Si atoms in holes of Te chains and a random substitution model, where the Te atoms and the Si atoms have the same short-range order, both show a concentration dependence of the areas F 1 contrary to the experimental values. A structural model which assumes the tetrahedron configuration of Si 2Te 3 for Si atoms (coordination number N Si = 4) and a coordination number N Te = 2 for Te atoms can describe the short-range order of glassy TeSi alloys in the whole investigated concentration range with 10–40 at% Si.