Analyses of intrinsic inhomogeneity and metal segregation in samples of Ag–Ge–Se glasses

Abstract

Ge y Se (1―y) glasses are semiconductors but when Ag is added above certain threshold concentration, Ag x [Ge y Se (1―y) ] (100―x) glasses behave as fast ionic conductors [Urena et al., Solid State lonics 176 (2005) 505]. This peculiar behavior may be attributed to the intrinsically inhomogeneous nature of these glasses where zones rich in metals coexist with zones of the host material. The conductivity transformation may be ascribed to the percolation of the Ag rich phase [Pradel et al., J. Phys.: Condens. Matter 15 (2003) S1561]. Ag x [Ge 0.25 Se 0.75 ] (100―x) glasses either massive or as films were obtained by melt quenching and pulsed laser deposition (PLD), respectively, in compositions belonging to the Se rich corner of the ternary phase diagram. Their amorphous nature and intermediate range order was checked employing X-ray diffractometry (XRD), the short range order was characterized by extended X-ray absorption fine structure (EXAFS) (Ge and Se K absorption edge) and their microstructure was characterized by scanning electron microscopy (SEM) and small angle X-ray scattering (SAXS).