Effect of Ag on the X-ray K-absorption edge of glassy Ga30Se70

The shift of the K-absorption edge, ΔE_k, is measured in ternary alloys of Ga₉₀Se_70?xAg_x (x=0, 5, 10, 15, 20) with respect to the binary Ga₉₀Se₇₀ alloy. The K-edge of Se progressively shifts towards the lower energy side as the silver concentration increases from 0 to 10 at.%. However, at higher concentration, it is observed that the relative shift starts decreasing. The present results follow Pauling's concepts of electronegativity which indicate that the nature of the bond is ionic-covalent in these glasses as found in many crystalline solids. The composition dependence of the edge shift is also discussed in terms of the structure of Se---Ga system.