Detection of H+ recoiled from Si(111)-1 x 1-H by medium energy Ne+ impact

We detected the H+ ions recoiled from Si(111)-1 x 1-H by medium energy 80-150 keV 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 similar to 70 degrees and almost 100% for emerging energy above 13 keV. In contrast, the charge state is not equilibrated even at similar to 85 degrees. 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 x 10(12) atoms/cm(2) at a small emerging angle (0(out) < similar to 75), where the H+ fraction reaches similar to 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. (C) 2012 Elsevier B.V. All rights reserved.