Role of water and oxygen in wet and dry oxidation of diamond

The wetting properties of diamond surfaces have been theoretically and expe rimentally investigated in the temperature range of 200-700 degreesC. It wa s experimentally observed that the conversion from hydrophobic to hydrophil ic surfaces will be more efficient with an increase in temperature when usi ng a mixture of H2O and O-2 in a wet-oxidation furnace, or only O-2 in a dr y-oxidation furnace. This conversion is especially efficient at temperature s higher than 400 degreesC. Molecular dynamic simulations of the wet- and d ry-oxidation processes at 450 degreesC, together with a more thorough theor etical quantum mechanical study of various important adsorption processes a t zero K, resulted in two favorable adsorption processes, dissociative adso rption of H2O and O-2, respectively. Surface reactions including gaseous H2 O were found to be responsible for the large hydrophilic properties of diam ond surfaces at lower temperature, while the corresponding surface reaction s including gaseous O-2 species were most probably the dominant ones at hig her temperatures. These results were strongly supported by the comparative experiments presented in this article. (C) 2001 American Institute of Physi cs.