Adsorption of K on Si(100)2×1 at room temperature studied with photoelectron spectroscopy

Publisher Website
Google Scholar
Abstract
Different coverages of K on the Si(100)2×1 surface were studied by photoelectron spectroscopy up to saturation coverage. The K 3p spectra show two components for coverages larger than 50% of saturation, which is consistent with the double-layer model. The Si 2p spectrum at saturation coverage shows a strong, well-resolved, K-induced component, with an energy shift of ∼0.42 eV, toward lower binding energies. Based on its intensity and the 2×1 periodicity observed by low-energy electron diffraction (LEED) this component is assigned to Si atoms forming symmetric dimers on the surface. An abrupt decrease of the band bending at the surface of the n-type sample by ∼0.23 eV, accompanied by the appearance of a surface state peak at the Fermi level, was observed for the initial growth. This peak is interpreted as due to a partial occupation of an empty surface band existing already for the clean surface. The smeared out appearance of the Si 2p core-level spectra for the smaller K exposures indicates that multiple surface shifts due to an inhomogeneous surface are present. For a coverage of about 30% of the saturation coverage, a sharpening of the line shape of the Si 2p spectra occurred and a 2×3 LEED pattern was observed, implying an ordering of the surface. At saturation coverage, another abrupt energy shift of the spectra, by ∼0.2 eV, occurred toward higher binding energies. This shift coincides with a metallization of the surface, which has been reported in inverse and direct photoemission studies.