Low energy electron diffraction and X-ray photoelectron diffraction study of the Cs/Si(001) surface: dependence on Cs coverage

Abstract

Cs adsorption on a wide-terrace single-domain Si(001) surface has been studied by low-energy electron diffraction (LEED) and X-ray photoelectron diffraction (XPD) as a function of Cs coverage (θ) and substrate temperature ( T S). For T S's of ~ 110 and ~ 320 K, several surface periodicities are found which have not been reported before for this system. Azimuthal Cs3d XPD patterns have been measured for most of the ordered surfaces. An XPD structure analysis is made for a streak × 3 surface at θ = 1 6 ML, in which a dilute arrangement of Cs atoms is deduced. An XPD structure analysis is made for the surfaces at θ = 1 3 ML taking into account a reversible transition between 2 × 6 and 2 × 3 for T S's of ∼ 110 and ∼ 320 K, respectively. A Cs dimer model is deduced in which a modulation of atomic positions into a 2 × 6 surface is averaged in the 2 × 3 surface but is fixed in a regular way in the 2 × 6 surface.