Tendency towards crystallization of Ge-As-Te system glasses

Abstract

Recently, in the field of the physics of condensed systems, of special importance are investigations concerning the problem of the application of materials with predetermined, i.e. predictable, characteristics. Fundamental investigations of complex noncrystalline semiconductors have revealed some specificities of their spectral, optical refractive, photo-optical, elasto-optical and electrophysical properties. Of special importance are the materials containing chalcogenic elements (S, Se, Te), as the nature of the chalcogen and the character of the bonds formed in glasses of this type offer possibilities of varying relevant parameters of the obtained materials. In the frame of our systematic investigations of three-, fourand five-component glass systems, involving first of all S and Se [1-4], the aim of this work is to present some of the results of X-ray characterization of Te-containing glasses. Glasses of the type (AssoTes0)x (GelsTe85)t00-x were obtained by synthesis from high-purity elementary components involving heating in sealed evacuated quartz ampoules for many hours. Maximum temperature of synthesis was 950 °C, and the melt was held at this temperature for 20-25 h. Having in mind the fact that the area of glassy state of the Ge-As-Te system is relatively small, and that Te-containing glasses exhibit an increased tendency towards crystallization [5, 6], the process of melt cooling was carried out by annealing in cold water. To obtain more complete information about the relevant structural units of the three-component system, glass of stoichiometric composition As2Te3 and glass with equal percentage content of the components AsTe have been prepared by an analogous synthetic procedure. X-ray studies were performed using an automatic powder diffractometer PW 1373-PW 1065/50 (Philips) with high temperature attachment HTK 10 (Paar) and automatic control bar HTK 2-HC (Paar). Experiments were carried out up to a maximum temperature of 500 °C. The rate of sample heating was 1 or 2 °C/min. Fig. 1 shows X-ray diffraction spectra for two samples of the investigated three-component system at a number of characteristic temperatures. The amorphous character of the synthesized materials has been confirmed by the absence of maxima in the diffraction spectra of thermally untreated samples (curves 1 in Fig. l a and b).