Adsorption of Rb on Si(100)2x1 at room temperature studied with photoelectron spectroscopy

Photoelectron spectra of the Si and Rb core-levels have been analyzed for increasing Rb coverage, At the initial stage of adsorption, an abrupt decrease of the band bending at the surface of the n-type sample by similar to 0.3 eV was observed, which is due to a partial occupation of an empty surface band existing already for the clean surface. A 2 X 3 low-energy electron diffraction (LEED) pattern was observed for coverages of about 1/3 of the saturation coverage, The Rb4p and 3d spectra show two components for further Rb adsorption, which provide evidence for two Rb adsorption sites supporting the so-called double-layer model. At saturation coverage, the surface shows a 2 X 1 periodicity in LEED due to the underlying Si dimer reconstruction. In the Si2p spectra a well resolved structure on the lower binding energy side with an energy shift of similar to 0.48 eV is identified as due to Si dimers bonding to the Rb atoms, In the Rb core-level spectra two components, separated by similar to 0.55 eV with approximately the same emission intensity, are well resolved in both 4p and 3d core-level spectra. A comparison to other alkali-metal-saturated 2X1 surfaces (Na, K and Cs) is also presented. (C) 1998 Elsevier Science B.V.