Si-H and C-H bond breaking during MeV-ion bombardment of a native oxide of silicon

We have studied the native oxide of silicon (110) and the changes produced by MeV-ion bombardment. The number of Si atoms incorporated in the oxide was measured using transmission channeling of 5.9 Mev 9Be ions through a thin Si sample. Concentrations of adsorbed H, C and O were measured using ion scattering and elastic recoil detection analysis (ERDA) techniques. The native oxide was found to be composed of 1/2 monolayer each of Si and O, with several monolayers each of H and C. Continued 9Be ion bombardment was found to increase the amount of Si in the oxide, up to a saturation value of one monolayer. The O concentration increased with dose, so that the ratio of Si to O in the oxide remained approximately one. An exponential decrease in the H concentration was observed, with the concentration approaching roughly one monolayer at large doses. A Si native oxide at the interface of a (thick) Si wafer and a 220 A Ag layer was studied using 58 MeV Cu ion bombardment at a glancing angle through the Ag layer. The concentrations of H, C and O were measured using ERDA. In this case, the H concentration also decreased exponentially with ion dose. These results will be discussed in terms of possible irradiation-induced chemistry in the native oxide. (orig.)