Structure of ultra-thin silicon film on HOPG studied by polarization-dependence of X-ray absorption fine structure

Structures of mono-layered silicon on a highly oriented pyrolytic graphite (HOPG) have been investigated by X-ray photoelectron spectroscopy and X-ray absorption near edge structure (XANES). For the Si K-edge XANES spectrum of the 0.15 mono-layered film, two distinct peaks were observed, which were assigned to the resonant excitations from the Si 1s into the valence unoccupied orbitals with π∗ and σ∗ characters. On the basis of the polarization dependences of the peak intensities, it was concluded that a part of the Si film lies flat on the HOPG surface, which supports the existence of two-dimensional graphene-like structure in mono-layered silicon.