Effect of silicon impurity on carbon nitride films prepared by microwave plasma chemical vapor deposition

Carbon nitride thin films have been synthesized on polycrystalline Pt substrates using microwave plasma chemical vapor deposition (MPCVD) technique. The effect of Si on the composition and structure of carbon nitride films was investigated using scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) patterns, Fourier transform infrared (FTIR) and Raman spectra. Small amounts of Si can increase the [N]/([C]+[Si]) atomic ratio and promote the crystallization of carbon nitride films. The [N]/([C]+[Si]) atomic ratio of carbon nitride film containing 5.52% Si can reach 1.35 which, is close to the stoichiometric value 1.33 of C3N4. The experimental XRD pattern contains all the strong peaks of α-C3N4 and β-C3N4. The films are mixtures of α-C3N4 and β-C3N4. The observed Raman and FT-IR spectra support the existence of CN covalent bond in carbon nitride compound.