Potassium adsorption on the Si(100)(2×1) surface studied by Si and K core level photoemission and photoabsorption spectroscopy

The questions of K–Si bonding and the K adsorption site of the K/Si(100)(2×1) surface system are studied by Si and K 2p core level photoabsorption and photoemission spectroscopy as a function of K coverage and incident x-ray polarization. An unoccupied K 4s derived surface state is found in the K L-edge spectra that is coverage as wen as polarization dependent. It is also found that the π* state of the surface Si dimer is eliminated by the potassium adsorption, indicating that there is some degree of charge transfer from K to the substrate. The K–Si bond is thus characterized as ofmixed covalent/ionic type. The polarization dependence suggests that the Si–K bond is inclined towards the surface plane.