Mechanisms of concurrent SiO desorption with oxide layer formation at Si(001) surface

Teraoka, Yuden; Yoshigoe, Akitaka ; Moritani, Kosuke*

Oxidation reactions at Si(001) surfaces has 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 O molecular beams in the temperature range from 900K to 1300K. With increasing an incident energy in the temperature range from 900K to 1000K, the SiO desorption yield decreased. In that case, the time evolution of an Si 2p photoemission spectrum showed that SiO structure at the surface was easily formed by the action of larger incident energy and the increased SiO coverage correlated with the decreased SiO desorption yield. Coincidence measurements of Si 2p photoemission spectra and SiO desorption yield revealed that the decrease of SiO correlated with the increase of Si component, and the SiO desorption was terminated at the oxide thickness of 0.22nm. These facts indicate that the SiO desorption take place at the topmost Si dimmers and its precursor is so called T site, in which O atoms are bonding to the dangling bonds of the dimmers. Consequently, M1 and M2 in the Dual-Oxide-Species (DOS) model were clarified to be T sites and Si states, respectively.