Electrical properties of nitrogen incorporated nanocrystalline diamond films

A series of nitrogen incorporated nanocrystalline diamond (ND) films were synthesized by microwave plasma-enhanced chemical vapor deposition (MP CVD) in a gas mixture of CH4/H2/N2 with varying nitrogen concentration in a wide range (0–75%). The phase composition, structure, and morphology of these ND films were systematically studied by using UV and visible Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). It was found that the sp2/sp3 ratio of carbon bonds increased, and the grain size decreased with the increase of nitrogen concentration in plasma. A peak located at ∼ 1190 cm− 1 was observed in visible Raman spectra. Based on the correlation between its intensity and the nitrogen concentration in plasma, the origin of this peak was discussed. The current–voltage (I–V) measurements showed a dramatic decrease of the resistivity of nanocrystalline diamonds due to the nitrogen incorporation, and the dependence of the resistivity on the nitrogen concentration was revealed.