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Thermal oxidizing treatments of hydrogenated diamond surfaces have been performed in an O2 environment.Chemisorption of oxygen on diamond surfaces has been investigated by diffuse reflectance Fourier-transform infrared (FTIR), temperature-programmed desorption (TPD), temperature-programmed reaction (TPR) and thermogravimetry (TG). Oxidation of the hydrogenated diamond occurred above 300 "C and diamond started to burn out above 480 "C in 20% 0,. Diffuse reflectance FTIR spectra indicated that the oxidation gave species containing C -0 and C-0-C structures on t h e diamond surface above 300°C. The structures of t h e chemisorbed species changed with the oxidation temperature. The maximum coverage of oxygen was obtained between 480 and 500 "C. TPD spectra of oxidized diamond indicated that the oxygencontaining species were desorbed as CO and CO, above 480°C. This paper deals with t h e mechanistic considerations for the oxidation of diamond surfaces.

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The chemisorbed species on diamond surfaces have been studied by Fourier-transform infrared (FTIR), temperature-programmed desorption (TPD) and laser Raman spectroscopy. Oxidized diamond powders were treated thermally in an H, environment. IR spectral changes were followed during the hydrogenation of oxidized diamond powders. We observed CH bonding on diamond surfaces. The amount of CH bonding increased with the temperature of treatment below 900°C. Above 9OO"C, the amount of the CH bonding decreased. Thermally desorbed species were analysed by mass spectrometry. H, was desorbed from hydrogenated diamond powders above ca. 800°C. Close agreement between FTIR and TPD results was obtained. Raman spectra indicated that the disordered graphitic carbon phase was formed above 900 "C.

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