Separation of vibrational and static disorder in amorphous In–Se films by EXAFS

Abstract

Configurational disorder in amorphous In–Se films containing 50, 60 and 66at.% Se, prepared by thermal evaporation in vacuum was studied by the extended X-ray absorption fine structure technique at both In and Se K-edges at 20 and 300K. The thermal vibration and static displacements have been separated using a standard processing procedure based on the Marquardt–Levenberg least squares method for two data sets, measured for each composition at low and room temperatures, based on an assumption that the thermal component of the Debye–Waller factor at 20K is substantially smaller when compared with the static one. Analysis of disorder effects on the local structure reveals static disorder contribution having greater influence on atomic displacements from their equilibrium positions than that resulting from thermal vibrations. Obtained coordination numbers suggest a certain degree of chemical disorder in the investigated indium selenide films.