Detection of H+ recoiled from Si(1 1 1)–1 × 1-H by medium energy Ne+ impact

Abstract

We detected the H+ ions recoiled from Si(111)–1×1-H by medium energy 80–150keV Ne+ impacts. The H+ fraction is dependent on emerging angle and emerging energy. With decreasing the emerging angle scaled from the surface normal the H+ fraction increases and reaches a saturation below ∼70° and almost 100% for emerging energy above 13keV. In contrast, the charge state is not equilibrated even at ∼85°. Such strong dependence on emerging angle is due to the location of H bound by Si atoms on top of the surface. The sensitivity to H on the surfaces is estimated to be better than 5×1012atoms/cm2 at a small emerging angle (θout<∼75°), where the H+ fraction reaches ∼100%. The unexpectedly large energy spread for the recoiled H+ spectra is attributed to the Doppler broadening caused by the zero-point energy of the vibrating H–Si system and additionally to small energy transfers among the three bodies of Ne+ and H–Si, although the assumption of binary collision between Ne+ and H is approximately valid. This H detection technique can be widely applied to analysis of chemical reactions including adsorption and desorption mediated by water and hydroxyl on various kinds of metal-oxide surfaces.