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.