Reinterpretation of the molecular O2 chemisorbate in the initial oxidation of the si(111)7 x 7 surface.
The initial oxygen adsorption on the Si(111)7 x 7 surface was investigated by high-resolution x-ray absorption spectroscopy. Below 220 K, a molecular adsorption species is identified by distinctive absorption resonances due to the 1 pi(g) molecular orbitals. The molecular species is metastabilized to have a lifetime of 15-35 min at 135 K only with the presence of atomic adsorbates of more than 0. 1 ML (monolayer). It is thus clearly evidenced that the very initial adsorption is dissociative even at 100 K and the molecular species is not a precursor state. The molecular adsorption structures with the coadsorbed oxygen atoms are suggested.
Matsui
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Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan.
Yeom
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Amemiya
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Tono
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Ohta
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