Structure of amorphous GexSe1−x and GexSeyZnz thin films: an EXAFS study

Extended X-ray absorption fine structure (EXAFS) measurements have been made on thin films of a-GexSe1−x with 0.2<x<1. The results show that the Ge–Ge, Ge–Se and Se–Se bond lengths have values 2.45, 2.37 and 2.32 (all ±0.03) Å, respectively and are independent of film composition. The partial atomic coordination numbers of Ge and Se suggest that the films have a predominantly chemically ordered 4-2 coordinated covalent bond network structure throughout the whole composition range, as found by others for Ge–Se bulk glasses with x<0.4. EXAFS data for a-GexSeyZnz films show that the lengths of Ge–Zn and Se–Zn bonds are 2.57±0.05 and 2.44±0.03 Å, independent of the composition. Results on the atomic coordinations reveal that Zn is fourfold coordinated and preferentially bonds to Se atoms.