Time resolved photoemission spectroscopy on Si( [formula omitted])-2 × 1 surface during oxidation controlled by translational kinetic energy of O 2 at room temperature

Abstract

We have experimentally studied the dissociative adsorption of O 2 on a clean Si(0 0 1)-2 × 1 surface at room temperature from the viewpoint of time resolved photoemission spectroscopy for surface chemical reactions induced by the O 2 incident energy. Combining the high-resolution and intense synchrotron radiation with the supersonic molecular beams technique, we have succeeded in the analysis of the time evolution of Si oxidation states (Si 1+, Si 2+, Si 3+ and Si 4+) induced by the translational kinetic energy of O 2 ( Et O 2 =0.04, 0.6, 2.0 and 3.0 eV). Furthermore, we proposed that the oxidation on a clean Si(0 0 1)-2 × 1 surface progressed in the mechanism of almost consecutive Si oxidation in the low translational kinetic energy region. It was found that the translational kinetic energy of O 2 induced the adsorption of oxygen atom at the bridge site between the Si dimer and at the backbonds of the Si dimers and the subsurface.