Partial density of valence states of amorphous and crystalline AgInTe2and CuInS2

Abstract

Measurements of the energy-distribution curves of photoemitted electrons were made for amorphous and crystalline samples of AgIn${\mathrm{Te}}_2$ and CuIn${\mathrm{S}}_2$. The energies of the exciting photons were 21.2 eV (He I), 40.8 and 48.4 eV (He II), 16.8 eV (Ne I), 26.9 eV (Ne II), and 1486.6 eV (A1 $\mathrm{K}\alpha$). The crystalline and amorphous samples were in the form of thin sputtered films, although, to demonstrate consistency, some measurements were also performed on bulk samples with A1 $\mathrm{K}\alpha$ radiation. It is shown that the obtained photoelectron-distribution curves represent the heavy $d$ admixture present in the valence bands. They can be decomposed into approximate partial $p$ and $d$ densities of valence states by using atomic cross sections for the corresponding partial excitation probabilities. These results are compared with information available on $p-d$ mixing based on the spin-orbit splitting of the band-edge excitons. The binding energies of the outermost core levels of the constituent atoms and their core shifts are presented. The energy of the valence plasmons is found to be 13.3 eV for AgIn${\mathrm{Te}}_2$ and 16.6 eV for CuIn${\mathrm{S}}_2$. These plasma frequencies contain a negligible contribution of the $d$ electrons.