Initial Products in the Oxidation of Si(111)-7×7 Surface Using O2 at 300 K and Those Formation Processes Observed by Real-time Synchrotron Radiation X-ray Photoelectron Spectroscopy

Abstract

To understand reaction mechanism of the oxidation at an Si(111)-7×7 surface using O2 at 300 K, the determination of initial products is essentially important. Oxygen bonding configurations and silicon oxidation states were observed using real-time X-ray photoelectron spectroscopy for O 1s together with Si 2p. It is found that ins structure initially forms, where one oxygen atom inserts in the backbond of Si adatom. It is ascertained that the chemisorbed molecular oxygen, so-called paul oxygen, is the adsorbate on top of the ins structure. It is also clarified that ad-ins structure and ins-tri structure, where ad means an oxygen atom on top of Si atom and tri means the interstitial oxygen atom, appear after a short time. Our results imply the presence of a mobile O2 on the surface.