Role of coverage on the electronic properties of sulfur chemisorbed on Cu(100): Ab initio calculations

We present an ab initio study of the electronic properties of the S/Cu(100) surface, with sulfur chemisorbed in the c(2x2) geometry, and compare it with the p(2x2) phase. We find that the two geometries, observed, respectively, at 0.5 ML and 0.25 ML of sulfur coverage, affect both the density of states and the dispersion and charge distribution of the hybrid S-Cu electronic states. The same superstructures occur under suitable experimental conditions also when organic molecules containing a sulfur atom as a headgroup, like MBO and CH3S, are chemisorbed on Cu(100). We show that the electronic properties of the S-Cu hybrid in simple S/Cu(100) may be used to interpret succesfully the experimental results of these two complex molecular systems.