Cluster-Cluster Interactions in A-GERMANIUM(1-X) TIN(X)SELENIUM(2)
Abstract
Cluster-cluster interactions were examined in the chalcogenide glasses, a-Ge_{1-x}Sn_{x} Se_2. These glasses consist of tetrahedrally-bonded rafts and ethanelike chains. Low temperature (77K) Mossbauer spectroscopy was used to examine the substitution of Sn for Ge in a-Ge_{ 1-x}Sn_{x}Se_2 for the range of concentrations 0.20 <=q x <=q 0.60. The results of this experiment showed that, for the entire range of concentrations examined, the Sn atoms preferentially substitute for the Ge atoms in sites on edges of the tetrahedrally-bonded rafts. The size of the rafts at each concentration was determined. Because the rafts in the glasses retain the short and intermediate range order of the layers in the crystalline counterparts, c-Ge_{1-x} Sn_{x}Se _2, high pressure techniques and Raman spectroscopy were used to examine the interaction between layers in two crystals, GeSe_2 and Ge_{0.8}Sn _{0.2}Se_2. The results showed that the vibrational modes associated with interlayer interactions are more sensitive to pressure than are modes which are primarily intralayer in nature. Mode Gruneisen parameters were calculated for the two crystals. A high pressure (.001 kbar <=q P < 70 kbar) Mossbauer study of a-Ge _{1-x}Sn_ {x}Se_2 was performed for x = 0.30 and x = 0.50. The primary result of this experiment was the detection of a low pressure region (P < 25 kbar) in which the intercluster interactions are changed, and a high pressure region (P > 25 kbar) in which the glasses are essentially three dimensional and the intracluster interactions are affected. This experiment provided evidence that the glasses are made up of distinct structural clusters, as shown by the different response to pressure of the rafts and ethanelike chains. The changes affected in the intralayer interaction were found to be much smaller than those changes measured in the interlayer interactions, confirming that the bonding within clusters is much stronger than the bonding between clusters.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1990
- Bibcode:
- 1990PhDT.......110P
- Keywords:
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- GERMANIUM TIN SELENIDE;
- Physics: Condensed Matter