Sulfur species at chalcopyrite (CuFeS₂) fracture surfaces

Pristine fractured surfaces of chalcopyrite (CuFeS₂) have been studied using Synchrotron Radiation X-ray Photoelectron Spectroscopy and conventional X-ray Photoelectron Spectroscopy. These high-resolution spectra reveal for the first time three distinct contributions to the S 2p spectrum. The main symmetric peak is located at 161.33 eV and is likely derived from fully coordinated bulk S atoms. A core-level shifted peak was observed at 160.84 eV and is attributed to surface monomeric species (S^2-). A second broad contribution at 161.88 eV likely represents surface polymeric species (S_n^2-). The data suggest that surface polymers form where S-terminated surfaces such as the (1̄11) plane are exposed during fracture.