Oxidation of deuterium-, acetylene-, and ethylene-terminated Si(100) by atomic oxygen

The oxidation of deuterium-, acetylene-, and ethylene-terminated Si(100) by gas-phase atomic oxygen is evaluated using Auger electron spectroscopy (AES). The atomic oxygen is generated by the 157 nm laser photolysis of O 2 , which results in nominally a 50/50 mix of the ground ( 3 P) and electronically excited ( 1 D) state species. O atom adsorption probabilities for oxygen coverages in the 1–3 ML regime are estimated to be on the order of 0.1 for these adlayer systems. For both C 2 H 2 and C 2 H 4 adlayers no effective loss of surface carbon is observed, indicating that there first must be extensive oxidation of the near-surface region of silicon (greater than about 3 ML) prior to the removal of chemisorbed carbon on Si(100). The O/Si AES ratio for the O atom oxidation for oxygen coverages of about 1–3 ML in the near-surface regime is found to be linear with O atom exposure for all three adlayers, with the propensity for reaction being given by the relative slopes of 1.0:1.4:2.0 for D-, C 2 H 2 -, and C 2 H 4 -terminated Si(100), respectively. The relatively low rate for O atom oxidation of D-terminated Si(100) suggests that the presence of defects facilitates the oxidation. While the difference in the oxidation rates for the C 2 H 2 and C 2 H 4 adlayers is statistically significant, this is most likely not due to initial adlayer coverage effects; the specific cause(s) of this difference, however, is not established.