Electronic structure of SnS deduced from photoelectron spectra and band-structure calculations

Abstract

SnS is a layer compound with a phase transition from a high-temperature \ensuremath{\beta} phase to a low-temperature \ensuremath{\alpha} phase with a lower symmetry. Ab initio band-structure calculations are presented for both phases. The calculations show that the charge distributions in the two phases are very similar. However, the band gap is much larger in the \ensuremath{\alpha} phase. The calculations are used to discuss the chemical bonding in the \ensuremath{\alpha} and the \ensuremath{\beta} phase. Energy-dependent photoelectron spectra, using synchrotron radiation, and angle-resolved photoelectron spectra were obtained for \ensuremath{\alpha}-SnS. The energy versus wave-vector curves deduced from the spectra are in good agreement with the band-structure calculations. Photoemission from the top of the valence band shows a resonance and an interference effect at photon energies of 25--30 eV.