ESD of H+ and D(+)by a two-electron process from hydrogen adlayers on Pt(111)

The electron stimulated desorption (ESD) behavior of H+ and D+ from a Pt(1 1 1) surface covered with dissociatively adsorbed hydrogen or deuterium has been investigated. Incident electron energies of 150 eV caused both the H and D+ ion yields to initially increase before finally decaying away. The position of the ion-yield maximum in the ion-yield curves exhibits a strong dependence on electron-beam current density, but little dependence on the initial H-2 or D-2 exposures. ion yield is seen to increase quadratically w ith electron-beam current density, indicating that ESD of H+ and D+ is a tw o-electron process. Kinetic energy distributions (KED) were also investigat ed. Comparison of the H+ and D+ ESD KED spectra clearly shows that the peak position for H+ KED is lower than that for D+ KED, and that H+ KED broaden to lower kinetic energy relative to D+ KED. The Menzel-Gomer-Redhead (MGR) model is used to develop a possible qualitative explanation of the differe nces observed in the ESD behavior for H+ and D+. Total removal cross-sectio ns were also measured for adsorbed hydrogen and deuterium, for which curren t density averaged cross-sections of Q(H) = (1.6 +/- 0.1) x 10(-16) cm(2) a nd Q(D) = (1.3 +/- 0.2) x 10(-16) cm(2) were obtained. (C) 1999 Elsevier Sc ience B.V. All rights reserved.