X-RAY SPECTROMETRY, VOL. 19, zyxwvutsr 243-245 (1990) Structural Studies of Glassy Semiconducting Se80 zyxw -x TezoInX Alloys Arvind Kumar and M. Husain Department of Physics, Jamia Millia Islamia, New Delhi, India S. Swamp, A. N. Nigam and A. Kumar Department of Physics, Harcourt Butler TechnologicalInstitute, Kanpur 208 002, India The shift of the K-abrption edge zyxwvutsr (AEd was measured in Seso-,Te201n,, where 0 zyxw < x < 20. It is ohserved that the K-edge of Se shifts progressively towards the lower energy side zyxwv as the In concentration increases from 0 to 15 at.-%. However, at higher concentrations, the relative shift starts to decrease. The results are in accordance with the Pauling concept of electrowgativity and indicate that the nature of the bonds is iono-covalent in tbese glasses, as found in many crystalline solids. The composition dependence of the edge shift is also discllssed in terms of the structure of the %Te system. INTRODUCTION Chalcogenide glasses are used as photographic materials and have therefore gained much importance. They are also used in various solid-state devices. The disadvantages of pure glassy Se, used for photographic drums, are its short lifetime and low sensitivity.' Certain additives are being used to overcome these difi- culties, and Se-Te binary alloys and some ternary alloys have created great interest owing to their greater hard- ness, higher photosensitivity, higher crystallization tem- perature, higher conductivity and smaller ageing effects compared with pure amorphous Se. X-ray spectroscopy is suitable for studying the nature of the bonding and electronic structure in non- crystalline solids2v3 where x-ray, electron and neutron diffraction techniques are inapplicable owing to the absence of sharp diffraction patterns. The addition of a third element to Se-Te alloys has been useful in understanding the structure and trans- port properties of chalcogenide glasses. In this work we studied the effect on the Se K-edge of the incorporation of In in a binary Se-Te glassy system. The results indi- cate that the shift of the Se K-edge is highly composi- tion dependent in the Seso-,Tezo In, system. EXPERIMENTAL Glassy alloys of Se,,-,Te,,In, with x = 0, zyxwvu 5, 10, 15 and 20 were prepared by a quenching technique. Pure (99.999%) materials (Se, Te and In) were weighed according to their atomic percentages and sealed in quartz ampoules (ca. 5 zyxwvutsr cm x 8 mm id.) in a vacuum of ca. lo-' Torr. The ampoules were then placed in a furnace where the temperature was raised to 600°C at 3 4 ° C min-'. The ampoules were rocked for about 10 h at the maximum temperature to make the melt homogeneous. Quenching was done in ice-water. The glassy nature was verified by x-ray diffraction. The solidified substances were ground to make a fine powder, which was spread uniformly over a Cellophane adhesive tape to form an absorption screen. The thick- ness theoretically calculated to give the best spectra was slightly higher than the actual thickness used (15-20 mg A bent crystal transmission spectrograph, employing a high-quality mica sheet oriented to reflect from (100) planes and bent to a radius of 30 cm, was used to record the K-absorption edges of selenium. A sealed x-ray tube (Chiraina) with a copper target was used as a source of continuous radiation. The tube was operated at 30 kV and 5 mA with a power supply (Radon House, Calcutta). In addition to the Cu K lines, W L lines were emitted by the tube and these served as refer- ence lines for the absorption edge. The spectra were recorded on Ilford FP4 single-coated films and devel- oped using IPC-76 developer. W Ly, and the Br K-edge served to calibrate the Se K-edge. The spectra were scanned on a Carl Zeiss micro- photometer at a magnification of 100x. The records give a dispersion of 0.789 mA mm-'. The position of the K-absorption edge of selenium was measured at the inflection point of the edge. cm - 2). RESULTS AND DISCUSSION The experiment was calibrated using pure Se. The wave- length of the Se K-absorption edge agreed with that 0049-8246/90/050243-03 $05.00 zyxwvuts 0 1990 by John Wiley & Sons, Ltd. Received 14 March 1990 Accepted 9 June 1990