XPS study of silicon surface after ultra-low-energy ion implantation

Ultra-low-energy ion implantation of silicon with a hydrogen-terminated (001) surface was carried out using a mass-separated P-31(+) ion beam. The ion energy was 30 eV, the displacement energy of silicon, and the ion doses were 6 x 10(13) ions/cm(2). Annealing after the implantation was not carried out. The effects of ion implantation on the surface electrical state of silicon were investigated using X-ray photoelectron spectroscopy (XPS). The Si 2p peak position using XPS depends on the doping conditions, because the Fermi level of the hydrogen-terminated silicon surface is unpinned. The Si 2p peak position of the specimen after ion implantation at vacuum pressure of 3 x 10(-7) Pa was shifted to the higher energy region. It suggested the possibility of phosphorus doping in silicon without annealing. In the case of ion implantation at 5 x 10(-5) Pa, the Si 2p peak position was not shifted, and the peak was broadened because of the damage by the fast neutrals. Ultra-low-energy ion doping can be achieved at ultra-high-vacuum conditions. (c) 2006 Elsevier B.V. All rights reserved.