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 with 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). The analysis of the EXAFS data is carried out by considering As–Te and As–X bonds for the As K edge and Ge–Te and Ge–X bonds at the Ge K edge, where X denotes As or Ge. For all the compositions, the Ge and As atoms are fourfold and threefold coordinated, respectively. Most of the Ge atoms are bonded to Te atoms although some Ge–X bonds are found even for Te-rich glasses. The As atoms and their three nearest neighbors form trigonal pyramids. The kind 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.