Mechanisms and dynamics of electron-stimulated desorption of D- from deuterated diamond surfaces: Surface versus subsurface stimulated desorption - art. no. 245417

In this work we report on a study of low-energy electron-stimulated desorpt ion (ESD) of D- from in situ hot-filament-deuterated surfaces of diamond fi lms. This deuteration procedure ensures that deuterium is predominantly ads orbed on the diamond surface and that no significant diffusion underneath t he surface takes place. For incident electron energies in the 5-35-eV range , dissociative electron attachment (DEA) and dipolar dissociation (DD) proc esses occur. The cross section for D- ESD obtains a maximum value at simila r to8 eV, whereas the DD process displays a threshold at similar to 14 eV. Ion kinetic-energy distribution (KED) measurements show that in the DEA reg ime desorption results in a narrow peak whose energy position increases wit h the incident electron energy to a value that corresponds, minus a multiph onon excitation factor, to the thermodynamic limit, in agreement with gas-p hase considerations. In the DD regime the ion KED displays a peak at simila r to2 eV which does not depend on the incident electron kinetic energy. To study the effect of inelastic interactions between the desorbing D- ions an d the surface, in the DEA regime, KED measurements were performed as a func tion of desorbing angle with respect to the surface normal. It was found th at with an increasing angle from the surface normal the D- KED broadens, an d its lower-energy component increases in intensity. These results clearly show that inelastic interaction between the outgoing D- and the solid surfa ce takes place, and determines the KED of desorbing ions. The ESD results o btained for the in situ deuterated surface are compared with those previous ly obtained for deuterated diamond films that contain some subsurface deute rium for which broad KED's were measured. A difference in the D- KED in the DD regime is also measured. The indirect DEA process observed in the case of hydrogenated (deuterated) diamond films is strongly reduced in the prese nt case of an on-top deuterated diamond surface. Our results show that ESD may be used to determine the presence of surface versus subsurface hydrogen (deuterium) adsorbed on diamond.