Correlation between metastable adsorbate and Si oxidation states in O adsorption on Si(111)-77 at room temperature

Yoshigoe, Akitaka ; Teraoka, Yuden

We found that the metastable adsorbate was assigned to be the molecularly adsorbate normally observed in oxygen adsorption process on Si(111)-77 at room temperature exsisting on Si adatoms having oxygen atoms at the backbond, thus it indicated that it is not precursor states in the dissociative adsorption process on clean Si(111)-77. Since the number of oxugen atoms at the backbond of Si adatom has not been clear due to only O1s XPS measurement, we studied the initial adsorption process based on the Si oxidation number by means of Si2p XPS measurement. All experiment were performed SUREAC2000 at BL23SU in SPring-8. The clean surface exposed in the oxygen gas ambient whose pressure was controlled by variable leak valve to be 5.310-7Pa. Real-time O1s and Si2p XPS measurement was performed. The Si oxidation states was clearly observed at the observable condition of metastable adsorbate in Si2p XPS. This result indiacates that the metastable adsorbates is assigned to be ins-paul structure. Furthemore, when the metastable adsorbate disappeared, the Si oxidation state was observed, thus the insx2-ad structure was formed via the oxygen dissociative process of ins-paul.