Orientation dependent adsorption on a cylindrical silicon crystal. II: Oxygen

Abstract The full orientation dependence of oxygen adsorption at temperatures between 350 and 870 K was investigated on a cylindrical Si sample using Auger electron spectroscopy and synchrotron radiation excited valence band and core level photoemission. At 350 K, bridge bonded atomic oxygen is adsorbed. However, also well below monolayer coverage oxygen begins to penetrate. At 350 K, the initial sticking coefficients are of the order of 0.2 for all orientations and decrease slightly at 670 K. Adsorption enhancement by steps is weak. The observed orientation dependence around and above 1 monolayer coverage is due to different oxygen penetration behaviours. Penetration is most effective at (111), followed by (001) and (112) and weakest at (110) and (113). The thickness of the SiSiO 2 interface after oxidation at 870 K. is of the order of 2 atomic layers and thus almost abrupt. The interface contains all oxidation intermediates Si + , Si 2+ and Si 3+ . The valence band, the O 2s and the Si 2p emission patterns show characteristic differences for atomically adsorbed oxygen, oxygen penetrated into the lattice and the oxide.