Electron-spectroscopic studies of the early stages of the oxidation of Si
- 15 April 1979
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review B
- Vol. 19 (8) , 3944-3956
- https://doi.org/10.1103/physrevb.19.3944
Abstract
Photoelectron spectroscopy (PES) and Auger electron spectroscopy have been used to study the early stages of the oxidation of the cleaved silicon (111) surface. The Si- core level as well as valence emission were studied with PES, using monochromatized synchrotron radiation at a photon energy which allows maximum surface sensitivity. In the initial adsorption stage (i.e., when the surface states are removed from the band gap), oxygen can be adsorbed either molecularly or atomically. The molecularly chemisorbed oxygen was characterized by a zero shift of the Si- core level, while the atomic state was associated with a 2.0-eV shift. Both types of chemisorption led to a removal of the filled surface states from the band gap. A third chemisorbed state, characterized by a 2.6-eV shift of the Si- core level, was observed in the adsorption stage beyond monolayer coverage. A broad 3.3-eV chemically shifted peak was attributed to Si atoms bonded to three oxygen atoms with smaller contributions from other states (i.e., Si and Si atoms bonded to one or two oxygen atoms). Finally, the formation of Si can be unambiguously identified by a 3.8-eV shifted peak. After an Si layer ∼ 12 Å thick had formed, asymmetric emission on the low-binding-energy side of the Si shifted peak revealed that approximately two layers of silicon atoms in the Si-Si interface were bonded to less than four oxygen atoms.
Keywords
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