Synthesis of nitrogen-doped diamond films by vibrational excitation of precursor molecules using CO2 laser in a combustion flame process

Abstract

Nitrogen (N) -doped diamond films were synthesized by resonantly exciting ammonia (NH3) molecules in ammonia-added oxyacetylene flames. A wavelength-tunable CO2 laser (spectrum range from 9.2 to 10.9 µm) was used for the resonant excitations. The NH wagging mode of the NH3 molecules was selected to achieve the resonant excitations. Both laser wavelengths of 10.591 and 9.219 µm were applied to the process. Compared with 10.591 µm produced by common commercial CO2 lasers, the laser wavelength of 9.219 µm proved much more effective in resonant excitation of the NH3 molecules. With a 500 W laser excitation at 9.219 µm, high quality N-doped diamond films were deposited with a doping level of 1.5×1020 N atoms/cm3. A morphologic transition from amorphous cauliflower structures to columnar diamond structures was observed before and after the resonant laser excitation. Potential growth mechanisms were investigated and discussed.Nitrogen (N) -doped diamond films were synthesized by resonantly exciting ammonia (NH3) molecules in ammonia-added oxyacetylene flames. A wavelength-tunable CO2 laser (spectrum range from 9.2 to 10.9 µm) was used for the resonant excitations. The NH wagging mode of the NH3 molecules was selected to achieve the resonant excitations. Both laser wavelengths of 10.591 and 9.219 µm were applied to the process. Compared with 10.591 µm produced by common commercial CO2 lasers, the laser wavelength of 9.219 µm proved much more effective in resonant excitation of the NH3 molecules. With a 500 W laser excitation at 9.219 µm, high quality N-doped diamond films were deposited with a doping level of 1.5×1020 N atoms/cm3. A morphologic transition from amorphous cauliflower structures to columnar diamond structures was observed before and after the resonant laser excitation. Potential growth mechanisms were investigated and discussed.