ELECTRON-IMPACT-INDUCED OXIDATION OF AL(111) IN WATER-VAPOR - RELATION TO THE CABRERA-MOTT MECHANISM

The oxidation of an A1(111) single-crystal surface induced by 100 eV e lectron bombardment in water vapor at room temperature has been studie d using x-ray photoemission spectroscopy and electron-energy-loss spec troscopy. Electron bombardment significantly increases the growth rate and changes the observed growth-rare law in comparison to the oxidati on without the electron beam, The aluminum oxide film grows with linea r rather than parabolic time-dependent kinetics up to a thickness of a bout 25 Angstrom. After reaching this thickness, the growth rare slows down significantly. During oxidation the oxide film becomes electrica lly charged on its surface and the normal electric field in the oxide remains constant. The results are discussed in the framework of a Cabr era-Mott type oxidation mechanism.