Network vs molecular structural characteristics of ge-doped arsenic sulfide glasses: A combined neutron/X-ray diffraction, extended x-ray absorption fine structure, and raman spectroscopic study
Journal of Physical Chemistry C, cilt.113, sa.15, ss.6231-6242, 2009 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 113 Sayı: 15
- Basım Tarihi: 2009
- Doi Numarası: 10.1021/jp810446g
- Dergi Adı: Journal of Physical Chemistry C
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
- Sayfa Sayıları: ss.6231-6242
- Boğaziçi Üniversitesi Adresli: Hayır
Özet
Combined neutron/X-ray diffraction, Ge and As K-edge extended X-ray absorption fine structure analysis, and Raman spectroscopy are employed to study the compositional dependence of the short- and intermediate-range structures of As-rich Ge xAs yS 100-x-y glasses with a constant Ge:As atomic ratio of 1:17.3. The structures of glasses with compositions near stoichiometry (35 ≤ x + y ≤ 43) are dominated by the presence of a predominantly heteropolar-bonded As 2S 3 network. However, an increasing metal content (x + y = 55) results in a novel glass consisting predominantly of AS 4S 3 molecules, held together by van der Waals forces. The formation of this "molecular" glass implies an apparently anomalous situation of near-zero connectivity and dimensionality with increasing average coordination number. A further increase in metal content (60 ≤ x + y ≤ 65) results in the formation of As - As homopolar-bonded structural regions that coexist with AS 4S 3 molecules. Such unusual evolution of intermediate-range order is shown to be closely related to the compositional variation of thermophysical properties and density fluctuation in these glasses. © 2009 American Chemical Society.