XPS study of lead on SiO x/Si: temperature and light effects

Abstract

Metal induced charge transfer from Si to Pb/SiO x is studied on Pb/SiO x /n-,p-Si(111) by XPS. The Si band bending and the influence of SiO x on the Pb/SiO x /Si surface sensitivity to light (X-ray and visible) are investigated at room and liquid nitrogen temperatures. The flow of positive charge through SiO x towards the sample surface is evidenced by a charge change on the oxide interlayer and Si band bending evolution with Pb deposition. At 300 K, the Si 2p reference binding energies reflecting the flattening of the bands are estimated to be 100.04 and 99.44 eV for our n- and p-Si substrates, respectively. The values of the Si band bending determined for the Pb/n-Si and Pb/SiO x /n-Si samples of about 0.22 eV are half of those for the samples on p-Si. However, nearly the same Schottky barrier height of about 0.58 eV is determined for both Pb/SiO x /n-,p-Si. At liquid nitrogen temperature, the oxide interlayer causes saturation of the surface photovoltage even at the lowest useful X-ray intensity.