Mechanisms of Concurrent SiO Desorption with Oxide Layer Formation at Si(001) Surface

Abstract

Oxidation reactions at Si(001) surfaces have been studied via real-time in-situ photoemission spectroscopy for chemical bonding states of Si and O atoms, and mass spectrometry for desorbing SiO molecules with synchrotron radiation and supersonic O₂ molecular beams in the temperature range from 900 K to 1300 K. In our previous studies, the SiO desorption yield decreased with increasing incident energy in the temperature range from 900 K to 1000 K,. In that case, the time evolutions of Si 2p photoemission spectra showed that SiO₂ structure on the surface was easily formed by the action of larger incident energy and the increased SiO₂ coverage correlated with the decreased SiO desorption yield. In this study, coincidence measurements of Si 2p photoemission spectra and SiO desorption yield revealed that the decrease of SiO correlated with the increase of Si²⁺ component, and the SiO desorption was terminated at the oxide thickness of 0.22 nm. These facts indicate that the SiO desorption takes place at the topmost Si dimmers and its precursor is so called T site, in which O atoms are bonding with the dangling bonds of the dimmers. Consequently, M1 and M2 in the Dual-Oxide-Species (DOS) model were clarified to be T sites and Si²⁺ states, respectively.