EXAFS study of the local structure in Ge-As-Te glasses

The local environment of the Ge and As atoms in Ge0.1AsxTe0.9-x, glasses wi th x = 0.15, 0.20, 0.46 and 0.54 has been investigated by X-ray absorption spectroscopy from the extended X-ray absorption fine structures (EXAFS), Th e analysis of the EXAFS data is carried out by considering As-Te and As-X b onds for the As K edge and Ge-Te and Ge-X bands at the Ge It edge, where X denotes As or Ge. For all the compositions, the Ge and As atoms are fourfol d and threefold coordinated, respectively. Most of the Ge atoms are bonded to Te atoms although some Ge-X bonds are found even for Te-lich glasses. Th e As atoms and their three nearest neighbors form trigonal pyramids. The ki nd of As neighbors changes strongly with the As content x and the number of As-Te bonds is found to decrease with increasing x. These results suggest chemical disorder around the Ge and As cations which is briefly discussed. (C) 2000 Elsevier Science B.V. All rights reserved.