Time resolved photoemission spectroscopy on Si(001)-2 x 1 surface during oxidation controlled by translational kinetic energy of O_2 at room temperature

摘要

We have experimentally studied the dissociative adsorption of O_2 on a clean Si(001)-2 x 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(00 l)-2 x 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.