Effect of Low Concentration of Nitrogen on Growth of Single Crystal Diamond

Monocrystalline diamond grains were synthesized by microwave plasma chemical vapor deposition with a mixture of CH₄, H₂ and N₂ gases.The diamond growth was monitored on line with photoemission spectroscopy.The effect of the addition of low N₂ concentration on the microstructures and properties of the diamond grains was investigated with Raman spectroscopy and scanning electron microscopy.The results show that the N₂ additionhad a major impact on the diamond synthesis.For example, as the N₂ -concentration increased, the deposition rate increased and the polycrystalline surface defects decreased, accompanied by a deterioration of crystallinity; a high N₂ -concentration resulted in graphite-phase formation.The shift to large wave numbers of the 1 st-order Raman peak and compressive stress were observed.An annealing in H₂ atmosphere did not fully release the N-impurity induced tensile stress in the N-doped diamond grains.