X-Ray Photoelectron Study of the Valence Bands in I–III–VI2 Compounds

The X-ray photoelectron spectra of the valence bands in CuAIS 2 , CuGaS 2 , CuInS 2 , and AgGaS 2 have been measured. The spectra show that the upper parts of the valence bands in the Cu-compounds and the lower part of the valence band in the Ag-compound are mainly composed of d states of the monovalent metals. The spectra have been deconvoluted with a measured instrumental response function. The deconvoluted spectra of the Cu-compounds show almost d-like bands whose locations well agree with those obtained from the optical study by Shay et al. Resemblance between the valence bands of the Cu-compounds and those of cuprous halides is pointed out. In the deconvoluted spectra of CuAIS 2 and CuGaS 2 , peaks which may be due to the states of the trivalent ions are found in the high-binding-energy parts.