Preparation and characterization of hydrogenated carbon nitride films synthesized by dual DC-RF plasma system

Carbon nitride films (CN_x films) were deposited on Si(1 0 0) substrates making use of dual direct current radio frequency (DC-RF) plasma enhanced chemical vapor deposition (PECVD), using a mixed gas of CH₄ and N₂ as the source gas. The microstructures, morphologies, and compositions of the resulting CN_x films were analyzed by means of atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transformation infrared spectrometry (FTIR), and Raman spectroscopy. The mechanical properties of the CN_x films were examined using a nano-indentation test system. The Raman spectrum showed two characteristic bands: A graphite G band and a disordered D band of carbon, which suggested the presence of an amorphous carbon matrix. FTIR and XPS measurements suggested the existence of C-NH, C=NH, C≡N, N-H, and C-H in the CN_x films, and the nitrogen to carbon atom ratio (N/C) is as much as 0.50. Moreover, the TEM showed various diffraction rings of different d values, which could confirm the polycrystallites embedded in the CN_x matrix. Besides, the quality and elasticity of the CN_x films were significantly improved by the incorporation of nitrogen. The films prepared in the present work had much higher hardness and Young's modulus than the DLC films prepared under the same conditions, and the elastic recovery parameter was up to 89%.