Elementary steps of the interaction of C:H film surfaces with thermal H/D atoms

The interaction of thermal H and D atoms with thin ion-beam deposited C:H films were studied with vibrational (HREELS) and Auger electron spectroscopy. At surfaces which exhibit aromatic sp2 CH groups a hydrogenation reaction towards sp3 is observed with a cross-section of 4.5 A2. At fully hydrogenated C:H surfaces with solely sp3 CH groups present, H abstraction towards molecular HD occurs at D impact with an initial cross-section of 0.05 A2. The magnitude of both cross-sections is in line with an Eley-Rideal mechanism. As a radical C atom is produced by the H abstraction reaction, a thermally activated de-excitation via a hydrocarbon radical split-off is initiated which causes chemical erosion of the C:H film at a yield of about 0.01C per incoming H around 600 K. (author)