Atomic and electronic structure of ZnS cleavage surfaces

Abstract

An ${\mathrm{sp}}^{3}$ model for ZnS is constructed and validated by comparison with optical absorption and photoemission data. It is used to predict the atomic and electronic structure of three cleavage surfaces of ZnS, zinc blende (110), and wurtzite (101\ifmmode\bar\else\textasciimacron\fi{}0) and (112\ifmmode\bar\else\textasciimacron\fi{}0). All three surfaces exhibit similar reconstructions: approximately bond-length-conserving relaxations in the top layer with the S species relaxing outwards. The perpendicular displacements of S atoms relative to Zn in the top layer are predicted to be 0.62, 0.67, and 0.62 A\r{}, respectively, for the three surfaces. Electronic surface states and surface resonances lead to considerable differences between the top-layer density of states and the bulk density of states. The model correctly predicts the measured surface atomic geometries and surface densities of states in the only case for which these quantities have been measured, i.e., the (110) surface of zinc-blende structure ZnS.