In Situ Photoemission Spectroscopy Using Synchrotron Radiation for O_2 Translational Kinetic Energy Induced Oxidation Processes of Partially-oxidized Si (001) Surfaces.

摘要

The influcence of translational kinetic energy of incident O_2 molecules for the passive oxidation process of partially-oxidized Si (001) surfaces has been studied by photoemission spectroscopy. The translational kinetic energy of O_2 molecules was controlled up to 3 eV by a supersonic seed beam technique using a high temperature nozzle. Two translational kinetic energy thresholds (1.0 eV and 2.6 eV) were found out in accordance with the first-principles calculation for the oxidation of clean surfaces. Si-2p photoemission spectra measured in representative translational kinetic energies revealed that the translational kinetic energy dependent oxidation of dimmers and the second layer (subsurface) backbonds were caused by the direct dissociative chemisorption of O_2 molecules. Moreover, the difference in chemical bonds for oxygen atoms was found out to be as low and high binding energy components in O-1s photoemission spectra. Especially, the low binding energy component increased with increasing the translational kinetic energy that indicates the translational kinetic energy induced oxidation in backbonds.