H+ photodesorption processes induced by inner-shell excitation from defective hydrogenated diamond films surfaces studied by synchrotron radiation

In the present work we study the mechanism of positive-hydrogen-ion photon- stimulated desorption (PSID) in the 280-310 eV photon energy range from def ective polycrystalline hydrogenated diamond film surfaces. Controlled effec t levels within the near surface were introduced by ion bombardment of hydr ogenated films. From a comparison between the PSID, the partial electron yi eld near-edge x-ray-absorption fine structure, and the low-energy secondary -electron emission, the mechanism of photodesorption from the ion-beam-dama ged diamond surfaces is discussed. The main effect of ion implantation on t he PSID of hydrogen ions is a change in the dominant mechanism of desorptio n. For ion-damaged diamond films, the desorption process promoted by direct C(1s)-sigma* excitation of carbon atoms bonded to hydrogen, C-H (ads), bec omes more efficient compared to the case of unimplanted diamond film. The i ndirect hydrogen desorption process proceeding through valence excitation o f C-H(ads) bonds by secondary electrons, dominant for an unimplanted hydrog enated diamond sample, strongly decreases for the ion-beam-irradiated surfa ces. This indirect process is the one that really characterizes H+ photodes orption from hydrogenated diamond surfaces. From the hydrogen PSID measurem ents we did not detect substantial removal of hydrogen from diamond films e xposed to ion irradiation at the energies and doses applied in this work.