SHORT-RANGE ORDER IN AMORPHOUS GE(SE1-XSX)2

X-ray diffraction in combination with the Raman scattering measurement in amorphous Ge(Se1-xSx)2 was conducted on a range of compositions. The first peak in the distribution function, g(r), is well resolved in all compositions and gives roughly four as the Ge coordination number, assuming that the peak contains only Ge-Se and Ge-S contributions, but not Se-Se, Se-S or S-S contributions. This result indicates that these glasses are all formed by mixed-anion AX4-nYn tetrahedral units (n = 0-4). The Raman symmetric stretching frequencies of five tetrahedral units observed in the spectra were determined on the basis of the VFF analysis to be 201 cm-1 for GeSe4, 225 cm-1 for GeSe3S1, 233 and 245 cm-1 for GeSe2S2, 271 cm-1 for GeSe1S3 and 345 cm-1 for GeS4 units.