Oxygen adsorption enhanced by translational kinetic energy of oxygen molecule on Si(111)-77 observed by real-time photoelectron spectroscopy using synchrotron radiation

Yoshigoe, Akitaka ; Teraoka, Yuden

It is known that the adsorption process of O on Si(111)-77 is changed by the translational kinetic energy (E): trapping-mediated adsorption mechanism occurs at lower than approximately 0.07eV and direct adsorption mechanism is dominate above 0.07eV. The adsorption mechanism is clarified through the E dependence of initial sticking probability, but the relation between time evolution of oxygen bonding configurations and E has not been understood. In this study, the role of E is investigated by real-time photoelectron spectroscopy using synchrotron radiation at room temperature. The time evolution is almost same as 0.03eV when the E is 0.07eV. This result suggests that trapping probability to precursor state dominates the initial adsorption process. On the other hand, the enhancement of formation rates of oxygen and the simultaneous creation of both Si and Si oxidation states are observed when E changes from 0.07eV to 0.15eV. This result implyes that the probability of direct adsorption for both molecularly chemisorption and dissociatively that increases without the reaction path of precursor states.