A SYNCHROTRON SI2P AND AS3D CORE-LEVEL STUDY OF THE AS-TERMINATED SI(001) SURFACE OXIDATION

The resistance of the As-terminated Si(001) surface to oxidation in O- 2 is the subject of this study. Photoemission spectra of As3d and Si2p core levels excited with synchrotron radiation reveals that spectral changes are evident, simultaneously for As and Si, only from similar t o 10(12) L (Langmuir) on, in stark contrast with a previous report ind icating a saturation coverage in the 400-2000 L range, Oxidation proce eds slowly, as dimerized As remain intact (similar to 24%) up to expos ures of similar to 10(13) L. In the oxidized areas, the four Si oxidat ion states (indicative of subsurface oxidation) and three As oxidation states plus metallic arsenic show up, This suggests a reduction of th e arsenic oxide by silicon, Arsenic losses are also observed, probably via sublimation of As4O6 molecules.