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 hydrogenated diamond film and Di(100) surfaces and amorphized diamond surface has been studied for incident photon energies in the 280-340 eV range. From comparison between the H+ yield as a function of photon energy and the near-edge x-ray absorption fine structure recorded by detecting secondary electrons of selected kinetic energies the processes leading to photodesorption are assessed. It is shown that desorption of H+ occurs through two different processes: an indirect process involving secondary electrons from the bulk and a surface process. The surface process is characterized by a resonance at 287.5 eV photon energy, which reveals the presence of C-H bonds on the diamond surface. Stimulated desorption of H- is mainly the result of indirect processes that involve secondary electrons. H+ photodesorption from an amorphized diamond surface can be also induced by C (1s) ionization. However, no H- desorption from the amorphized surface could be detected. We suggest that this effect is associated with the reduced secondary electron emission yield of the amorphized diamond surface. Our results demonstrate that ion photodesorption may be used as a sensitive probe for hydrogen on diamond surfaces. [S0163-1829(99)05603-9].