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

Carbon nitride films (CNx 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 CNx 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 CNx 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 CNH, CNH, CN, NH, and CH in the CNx 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 CNx matrix. Besides, the quality and elasticity of the CNx 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%.