INITIAL-STAGES OF OXIDATION OF HYDROGEN-TERMINATED SI SURFACE STORED IN AIR

We have investigated the oxidation of hydrogen-terminated Si(111) and (100) surfaces stored in air, using synchrotron radiation photoemissio n spectroscopy and infrared absorption spectroscopy in the multiple in ternal reflection geometry. We demonstrate that water present in air i s predominantly involved in the oxidation of the topmost layer of the hydrogen-terminated surface. We find that native oxide starts to grow when the surface hydrogen coverage diminishes. This trend is interpret ed in terms of a kinetic model of oxidation in which it is assumed tha t native oxide formation preferentially rakes place on the portion of the surface where surface Si atoms having Si-H bonds are oxidized.