An XPS study of the influence of impurity Cu on the electronic structure of SrS

In this work the influence of Cu on X-ray photoelectron Sr 3d and S 2p spectra for low Cu concentrations in SrS is studied. The Cu impurity in the SrS lattice is detected by SIMS and X-ray diffractometry. l analysis of the S 2p and Sr 3d spectra shows that the Cu impurity at concentrations less than the XPS sensitivity limit has its main influence on the S 2p doublets that correspond to sulphur in SrS and to elementary sulphur clusters. SrS doping by Cu with subsequent annealing is accompanied by a decrease in the sulphur clusters size and leads to downward band bending and/or n-doping of SrS.