Stimulated desorption of F{sup +} and Cl{sup +} from Si surfaces: Initial excitations and final-state effects
- Lawrence Berkeley National Lab., CA (United States)
Many photochemically-induced surface reactions result from stimulated desorption, in which a photon or electron induces an electronic excitation to a repulsive state, leading to the removal of a lightly-bound surface species. In this work, photon stimulated desorption (PSD) and electron stimulated desorption (ESD) of positive halogen ions from silicon surfaces are investigated in order to determine (1) which initial excitations give rise to ion desorption, and (2) how do ion-surface interactions affect the trajectory of the exiting ions? To investigate (1), the PSD yield of F{sup +} and Cl{sup +} ions from Si was measured as a function of the incident photon energy. It was found that for both adsorbed F and Cl, excitations of the anion lead to ion desorption. For cation excitations, however, ion desorption was observed only for F{sup +}. This discrepancy appears to be related to the ionicity of the original bond. For (2), ESD of Cl{sup +} from Si(111) was looked at first, as the yield is primarily along the surface normal. Angle-resolved kinetic energy distribution enabled determination of the image charge interaction strength and the anisotropy in ion neutralization. This method was then applied to Si(100), for which off-normal desorption occurs. It was found that the angular and energy distributions of desorbed F{sup +} and Cl{sup +} are markedly different. When ion-surface interactions are taken into account, however, the initial surface bond angles appear to be the same. The major difference between F{sup +} and Cl{sup +} is actually a much larger neutralization probability for Cl{sup +}, which severely distorts the measured ion distribution.
- OSTI ID:
- 539079
- Report Number(s):
- CONF-960807--
- Country of Publication:
- United States
- Language:
- English
Similar Records
Determination of molecular structure at surfaces using angle-resolved electron- and photon-stimulated desorption
Theoretical study of stimulated desorption of protons from transition metal surfaces