POSTDEPOSITIONAL DIAMOND ETCHING

Differently prepared polycrystalline vapour deposited diamond films were exposed to pure oxygen for well defined periods of time at 700-degrees-C in order to monitor their time-dependent oxidation by scanning electron microscopy (SEM), photoluminescence measurements, and Raman spectroscopy. Raman and SEM data reveal that defective diamond or non-diamond carbon components located at the grain boundaries of the polycrystalline material are preferentially etched. The time-dependences of both Raman and luminescence intensities help to separate oxidation-resistant from oxidation-sensitive films and indicate that the presence of an interconnected network rather than the absolute concentration of non-diamond carbon is important for the oxidation behaviour. Nitrogen-induced defects in the vapour deposited films, manifested by a 1.83 eV luminescence line, seems to promote the formation of such a network and, above a threshold level, drastically enhance the oxidation sensitivity of diamond deposits.