Core level photoelectron spectroscopy of LiGaS2 and Ga-S bonding in complex sulfides

The electronic parameters of the lithium thiogallate LiGaS2 have been evaluated by X-ray photoelectron spectroscopy (XPS). Spectral features of all constituent element core levels and Auger lines have been considered. The Ga-S bonding effects in Ga-bearing sulfide crystals have been discussed using binding energy difference Δ2p(S-Ga) = BE(S 2p) - BE(Ga 3d) as a representative parameter to quantify the valence electron shift from gallium to sulfur atoms. The value Δ2p(S-Ga) = 141.9 eV found for LiGaS2 is very close to that evaluated for AgGaS2. This relation is an indicator of closely coincident ionicity of Ga-S bonds in LiGaS2 and AgGaS2.