Chemical order in Ga or Sb modified germanium sulfide glasses around stoichiometry: High-resolution XPS and Raman studies

To understand the unique features of germanium sulfide (~60-70 at.% of S) glasses modified with Ga or Sb, the chemical order in these materials is investigated using X-ray photoelectron spectroscopy (XPS). The obtained results are correlated with Raman spectroscopy data and verified with quantum chemical calculations. It is shown that in addition to the regular corner-shared and SS-shared [SbS3/2] pyramids and [GeS4/2] tetrahedra, a fraction of these structural units can form edge-shared fragments. The obtained XPS results also support the possibility for [SbS5/2] distorted square pyramids formation in Sb-rich glasses. At higher concentrations of antimony, a tendency to the increased concentration of homopolar bonds is observed.