A study on initial oxidation of Si 100/-2=1 surfaces by coaxial impact collision ion scattering spectroscopy

By using coaxial impact collision ion scattering spectroscopy CAICISS., we have studied the structural changes extending over the first several layers from oxidized Si 100.-2=1 surfaces. A simulation of ion scattering was used for the analysis of CAICISS spectra. At an oxide thickness of 0.87 monolayer ML., a peak in the CAICISS spectrum, which originates from the first-layer Si atoms, disappears. This finding indicates that the first-layer Si atoms move due to the structural relaxation accompanying the adsorption of oxygen atoms onto Si`Si dimer sites and back-bond sites. In the CAICISS spectrum for 1.1-ML-thick oxide, some peaks appear due to the oxygen adsorption onto Si`Si bonds between the second- and the third-layer Si atoms. From this result, we can deduce that the inward oxidation occurs before the lateral oxidation finishes. q2000 Elsevier Science B.V. All rights reserved.