Nitrogen-doped diamond films

We found that very high concentrations (up to 20% vol) of nitrogen in the e thanol/hydrogen gas mixture do not prejudice the diamond quality as determi ned by Raman spectroscopy. Nitrogen addition also increases the diamond gro wth rate, as was previously reported at low nitrogen concentrations. We obs erved that after a second heating cycle in air at temperatures between 300 and 673 K the electrical resistance versus temperature curves of the as-gro wn films presented a bulk semiconductor behavior. This stabilization was du e to the oxidation of the as-grown hydrogenated surface. The electrical ion ization energy E-d was found to be in the range of 1.62-1.90 eV correspondi ng to films produced with 0 to 20% vol nitrogen in the feed. The room tempe rature photoluminescence spectra of films produced at low nitrogen concentr ation suggest that E-d results from pure electronic transitions in the nitr ogen-vacancy neutral defects; for samples produced with nitrogen concentrat ions in the range 15-20% vol the E-d values may be due to, among others, GR 1 "vibronic'' transitions and charged nitrogen-vacancy defects. (C) 1999 Am erican Institute of Physics. [S0021-8979(99)01710-7].