Atomic and electronic structure of theSi(001)−Rbchemisorption system at 0.5 and 1.0 monolayer coverage

Abstract

The atomic and electronic structure of the $\mathrm{Si}(001)\text{\ensuremath{-}}\mathrm{Rb}$ chemisorption system at 0.5 and 1.0 monolayer coverage has been investigated using the plane wave, pseudopotential density functional method contained in the VASP code. The atomic and electronic structures of the $\mathrm{Rb}$ chemisorption system at 0.5 monolayer coverage are found to be very similar to the $\mathrm{Li}$ chemisorption system at the same coverage. The minimum energy structure determined for the $\mathrm{Si}(001)\text{\ensuremath{-}}\mathrm{Rb}$ chemisorption system at $1.0\phantom{\rule{0.3em}{0ex}}\mathrm{ML}$ coverage has been found to be in good agreement with the x-ray standing-wave (XSW) field data. The predicted occupied and unoccupied electronic surface state bands have also been shown to be in excellent agreement with the ARUPS and IPES results. The calculations suggest that the bonding between the $\mathrm{Rb}$ adatoms and the $\mathrm{Si}$ substrate atoms is neither purely ionic nor covalent. No evidence has been found in support of strong $\mathrm{Rb}\text{\ensuremath{-}}\mathrm{Rb}$ interactions and the formation of a metallic overlayer.