Photon-stimulated desorption of H+ and H- ions from diamond surfaces: Evidence for direct and indirect processes

Photon-stimulated desorption of positive and negative hydrogen ions from hy drogenated diamond film and Di(100) surfaces and amorphized diamond surface has been studied for incident photon energies in the 280-340 eV range. Fro m comparison between the H+ yield as a function of photon energy and the ne ar-edge x-ray absorption fine structure recorded by detecting secondary ele ctrons of selected kinetic energies the processes leading to photodesorptio n are assessed. It is shown that desorption of H+ occurs through two differ ent processes: an indirect process involving secondary electrons from the b ulk and a surface process. The surface process is characterized by a resona nce at 287.5 eV photon energy, which reveals the presence of C-H bonds on t he diamond surface. Stimulated desorption of H- is mainly the result of ind irect processes that involve secondary electrons. H+ photodesorption from a n amorphized diamond surface can be also induced by C (1s) ionization. Howe ver, no H- desorption from the amorphized surface could be detected. We sug gest that this effect is associated with the reduced secondary electron emi ssion yield of the amorphized diamond surface. Our results demonstrate that ion photodesorption may be used as a sensitive probe for hydrogen on diamo nd surfaces. [S0163-1829(99)05603-9].