Electronic structure of a Pd monolayer on an Si (111) surface

The electronic structure of a model Si (111) surface with a Pd overlayer is investigated. The self-consistent pseudopotential method in the mixed basis set (Gaussian orbitals plus plane waves) representation is used to describe the system. Two different adsorption sites of Pd (the top site and the triangular site) studied here give different dispersions for the Pd d bands and different hybridization between Si and Pd atoms. The Pd d peak centers around -1.8 and -2.2 eV below the Si valence-band maximum in each case. Partially filled Pd-Si hybridized states exist in the gap. The Schottky barrier height is 1.1 eV for the top site and 0.95 eV for the triangular site, respectively. Various localized states are examined, and the behavior of the Schottky barrier is discussed. Comparisons with experiment are made when possible.