Sulfur K- and L-edge XANES and electronic structure of zinc, cadmium and mercury monosulfides: a comparative study

S K- and L-edge X-ray absorption near-edge structure (XANES) spectra of sphalerite (cubic ZnS), wurtzite (hexagonal ZnS), greenockite (hexagonal CdS), metacinnabar (cubic HgS) and cinnabar (trigonal HgS) have been obtained using synchrotron radiation. The near-edge features of the S K- and L-edge XANES are qualitatively interpreted based on the MO/energy band structures of these Zn, Cd and Hg monosulfides. The near-edge features reflect the density of the states (DOS) of unoccupied S 3s, 3p and 3d states in the conduction band (CB). From ZnS to CdS and HgS, the S K- and L-edges shift toward lower energy by about 2.3 and 1.8 eV, respectively, and the energy gap decreases by about 1.9 eV, indicating that the unoccupied S 3s and 3p states, and the CB minimum move down to lower energy. In transition metal sulfides, the bonding behaviour of Zn 3d10, Cd 4d10 and Hg 5d10 electrons is distinct, and also differs significantly from that of Fe3+ 3d and Cu+ 3d electrons, which have a stronger bonding interaction with sulfur. The Fe2+ 3d crystal field band in the fundamental gap of (Zn, Fe)S has been confirmed to have little DOS involving S 3s- and 3P-like states. For tetrahedrally coordinated sphalerite, wurtzite, greenockite and metacinnabar, the post-edge features of the S K- and L-edge XANES are linearly correlated with the reciprocal interatomic distances and lattice plane distances. Hence, the S K- and L-edge XANES of Zn, Cd and Hg monsulfides provide information on the local structure and coordination of sulfur atoms. The K-edge XANES of different anions in ZnS-structure compounds are qualitatively similar, and may be used as structural fingerprints for studying local structures of unknown materials, such as chalcogenides glasses and metalloproteins.