The room-temperature Raman spectra of bulk As-S and As-Se glasses have been recorded. The compositior studied range throughout the glass-forming regions but are mainly close to the stoichiometric composition As40X60 (X = S or S a): eleven compositions in the range As35X65 - As45S55 have been studied in each system. Polarisation measurements have been made on all the glasses and from them have been derived the depolarisation spectra. The frequencies and polarisation states of the bands in the a-As 40S60 and a-As 40Sefi0 spectra can be accounted for using the Lucovsky-Martin molecular model. It is found that the spectra of these two glasses scale by the same two factors that relate the spectra of the corresponding crystals. The applicability of the interlayer scale factor to the glass spectra supports the presence of layer regions in the glasses. The spectra on the chalcogen-rich side of the stoichiometric composition As40X60 have also been analysed in terms of the Lucovsky-Martin molecular model and indicate the replacement of the ASX-2.s links between the AsX3 pyramid units by AsX X-As links as the chalcogen content is increased. The presence of S8 rings is increasingly apparent in the sulphide compositions more S-rich than As 37S63. In the case of the As-rich sulphides sharp spectral features characteristic of the crystal p-As4S4 appear near stoichiometry and increase smoothly as the As content is increased through the limit of the glees-fo=ing region, -As 43S57, and on into the phase-separated region. The results also indicate that As4S3 or As4S5 molecules are present and that As-As bonds are formed in the glass network. In the case of the As-rich selenides, for the compositions between As40Se60 and As45Se55 the additional As atoms go mainly into the formation of As-As bonds in the network. For compositions containing more than 50 % As the production of As4Se4 molecules predominates over the formation of As-As bonds in the network, although these are still present.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:650429 |
| Date | January 1979 |
| Creators | Ewen, Peter John Spence |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14815 |
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