Chemical characteristics of Dy–S bonds in Ge–As–S glass

From Dy L₃-edge extended X-ray absorption fine structure spectroscopic analysis of Dy-doped Ge–As–S glass, we verified that both the coordination number and Dy–S distance are decreased in this representative chalcogenide glass compared to those in the Dy₂S₃ crystalline counterpart. The strong covalent nature inherent in chemical bonds between the constituent atoms of Ge–As–S glass would be responsible for the enhanced covalency of the Dy–S bonds, which would then be sensitively related to the optical characteristics of the 4f ↔ 4f transitions of Dy³⁺ as well as the low rare-earth solubility exhibited by the Ge–As–S glass.