Hydrogen ion desorption from amorphous carbon films induced by resonant core electron excitations

In order to get insight into the mechanism of structural change in tetrahedral amorphous carbon (ta-C) films that is induced by soft X-ray illumination at photon energies near the carbon core edge, the desorption of ions from ta-C films, as a possible process taking place concurrently with the photo-induced restructuring, was studied by time-of-flight (TOF) measurements of photo-ions as a function of photon energy. The results show that (1) the main ions detected are H+, (2) the desorption efficiency spectra exhibit a resonant peak at 286–287 eV which is common to all detected ions, and (3) is 3 eV lower than the resonant peak in the efficiency spectrum of photo-induced restructuring. These rule out the hypothesis that it is the photo-induced C–H bond rupture that causes the resonant soft X-ray-induced restructuring in ta-C films.