Investigation of the Effect Produced by Short-range and Long-range Order on the Spectrum of Valence Electrons in Solids

Abstract

X-ray photoelectron spectra of valence and core electrons are obtained for AgI, Ag2S, Ag2Se, Ag2Te, Ag2HgI4, Cu2HgI4 and Cu2S–compounds which reveal a lattice instability at temperature increase. X-ray photoelectron spectra of valence and core electrons in the chalkogenides AgAsS2, AgSbS2, and AsGeS in crystalline and glass-like states were studied. For AsGeS in crystalline and glass-like state the X-ray emission LII,III-spectra of sulphur were investigated. K- and LII,III-emission spectra of pure sulphur were also obtained. When the compounds go from the crystalline state into the α-phase, a smoothing takes place of structural singularities in the photoelectron spectra in the region of energy localization of the states of the non-metallic components. The structural singularities are clearly resolved in the X-ray photoelectron spectra of AgAsS2 and AgSbS2 crystals but are smoothed in the spectra of the glass-like state. The X-ray photoelectron spectrum of the glass-like state has two maxima near the valence band top while the spectrum of the crystal has only one maximum. For AsGeS in its glass-like state the singularities of the fine structure observed in the LII,III-emission spectrum of sulphur are less pronounced than in the corresponding spectrum of the crystalline state. When the investigated compounds of Ag and Cu go from the crystalline state into the α-phase and when the chalcogenides AgAsS2, AgSbS2, and AsGeS are transferred from the crystalline into the glass-like state the atom charge state does not undergo perceptible changes. The alterations observed in the X-ray photoelectron spectra when compounds transfer from a crystalline state into one with a lattice instability or into a glass-like state are due to the effect produced on the energy structure of valence electrons by the short- and long-range order in the arrangement of atoms of metal and nonmetal components in the compound.