The effect of phosphorus on the properties and structure of Ge As S glasses

Ge As P S glasses with a fixed Ge:As:P ratio of 5:1:1 and S contents ranging from 56 to 74% were synthesized. On reducing the S content, the absorption edge of these glasses remains constant until S deficits of 20-30% are attained. Raman spectra of stoichiometric and S-deficient glasses show bands attributed to As2 P2 S8 and (As, P)4 S3 species, respectively. NMR spectra of glasses with S deficits ≥ 10% have a 31 P resonance near-100 ppm, indicating that tetrahedral S+PS3/2 and trigonal PS3/2 groups are replaced by species containing P-P bonds as the S content of these glasses decreases. Comparison of these results with those for Ge As S glasses demonstrates that P-P bonds form preferentially to metal-metal bonds containing either Ge o As, and that P tends to associate with As instead of Ge as next nearest neighbors. (author)