Dissociative adsorption of molecular deuterium on polycrystalline diamond films activated by medium surface temperature

Abstract

In this work we report on an investigation of thermally induced dissociative adsorption of molecular deuterium onto hydrogenated and bare polycrystalline diamond film surfaces studied by high resolution electron energy loss spectroscopy (HR-EELS). Hydrogenated diamond films (grown from CH4 and H2 gases) were heated at various temperatures in molecular D2 ambient at 5× 10-6 Torr and then studied by HR-EELS. This study clearly shows the formation of C-D bonding on hydrogenated polycrystalline diamond surface and gradual disappearance of C-H mode as a function of annealing temperature. The C-D bonding configurations and thermal stability of adsorbed deuterium resulting from dissociate adsorption were compared to those occurring on deuterated diamond films (grown from CD4 and D2 gases). We report and assign at least three contributions to C-D stretching HR-EELS mode associated to (111), (100) crystallographic orientations as well as grain boundary associated vibrations in accordance with similar vibrations of C-H stretching vibrations, reported previously.