Vapour-phase oxidation of diamond surfaces in O2 studied by diffuse reflectance Fourier-transform infrared and temperture-programmed desorption spectroscopy

Abstract

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% O₂. Diffuse reflectance FTIR spectra indicated that the oxidation gave species containing CO and C—O—C structures on the diamond surface above 300 °C. The structures of the 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 oxygen-containing species were desorbed as CO and CO₂ above 480 °C. This paper deals with the mechanistic considerations for the oxidation of diamond surfaces.