In this paper, X-ray photoelectron and X-ray-excited
Auger electron spectroscopy was used to investigate the chemical
surface structure of CuInS2 thin-film solar cell absorbers.We find
that the [In]/[Cu] surface composition can vary between 1.6 (±0.4)
and 3.7 (±0.7), depending on relatively minor variations in the absorber
formation process and/or whether additional wet-chemical
treatments are performed. These variations are primarily due to
differences in the Cu surface concentration. The corresponding
change of the modified In Auger parameter is interpreted as being
indicative of a change in the chemical environment of In as a
function of Cu off-stoichiometry.