Local electronic and geometric structures of silicon atoms implanted in graphite

Low-energy Si+ ions were implanted in highly oriented pyrolitic graphite (HOPG) up to 1% of surface atomic concentration, and the local electronic and geometric structures around the silicon atoms were in situ investigated by means of the Si K-edge X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectroscopy using linearly polarized synchrotron radiation. The resonance peak appeared at 1839.5 eV in the Si K-edge XANES spectra for Si+-implanted HOPG. This energy is lower than those of the Si 1s --> sigma(*) resonance peaks in any other Si-containing materials. The intensity of the resonance peak showed strong polarization dependence, which suggests that the final state orbitals around the implanted Si atoms have pi*-Iike character. It is concluded that the sigma-type Si-C bonds produced by the Si+-ion implantation are nearly parallel to the graphite plane, and SixC phase forms two-dimensionally spread graphite-like layer with sp(2) bonds. (C) 2002 Elsevier Science B.V. All rights reserved.