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First-principles calculations based on DFT-GGA method have been performed on Rb adsorption on C(100)(2 x 1) surface. The optimized geometries, adsorption energies have been obtained and the preferred binding sites have been determined for the coverage (Theta) of one monolayer and half a monolayer. The calculated results have shown that Rb adsorbate preferred to occupy valley-bridge sites at the coverage of 0.5 ML. At higher coverage of 1 ML, two Rb adsorbates were found to reside in pedestal site and valley-bridge site, respectively. It was also found that when Rb was adsorbed on C(100)(2 x 1) surface the work function decreases linearly with increasing coverage and reaches a minimum at Theta = 0.5 ML, at higher coverage, the work function is increased again, which may be caused by depolarization effect of the adsorbate: The adsorption behavior was found to be similar to that of Rb on Si(001) and Ge(001) surface. (c) 2006 Elsevier B.V. All rights reserved.