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

Abstract

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 defective polycrystalline hydrogenated diamond film surfaces. Controlled defect levels within the near surface were introduced by ion bombardment of hydrogenated films. From a comparison between the PSID, the partial electron yield near-edge x-ray-absorption fine structure, and the low-energy secondary-electron emission, the mechanism of photodesorption from the ion-beam-damaged diamond surfaces is discussed. The main effect of ion implantation on the PSID of hydrogen ions is a change in the dominant mechanism of desorption. For ion-damaged diamond films, the desorption process promoted by direct $\mathrm{C}(1s)\ensuremath{-}{\ensuremath{\sigma}}^{*}$ excitation of carbon atoms bonded to hydrogen, C-H (ads), becomes more efficient compared to the case of unimplanted diamond film. The indirect hydrogen desorption process proceeding through valence excitation of C-H(ads) bonds by secondary electrons, dominant for an unimplanted hydrogenated diamond sample, strongly decreases for the ion-beam-irradiated surfaces. This indirect process is the one that really characterizes ${\mathrm{H}}^{+}$ photodesorption from hydrogenated diamond surfaces. From the hydrogen PSID measurements we did not detect substantial removal of hydrogen from diamond films exposed to ion irradiation at the energies and doses applied in this work.