Air oxidation of undoped and B-doped polycrystalline diamond films at high temperature

Air oxidation of undoped and B-doped polycrystalline diamond films was investigated at temperatures between 500 and 700 °C. Diamond (111) facets were etched for both undoped and B-doped films after 1 h at 700 °C. The etching rate of (111) facet due to oxidation was approximately 50% lower by B-doping of 1 × 10¹⁹ cm⁻³, presumably because of the decrease of sp² bands and lattice defects that were identified by Raman and photoluminescence spectroscopy. X-ray photoelectron and electron energy loss spectroscopy revealed that by the high temperature treatment, the diamond surface was initially converted into graphite and successively etched by oxygen.