On the structure and composition of crystalline carbon nitride films synthesized by microwave plasma chemical vapor deposition

Crystalline carbon nitride thin films were prepared on Si (100) substrates by a microwave plasma chemical vapor deposition (MPCVD) method, using CH4/N2 as precursor gases. The surface morphologies observed by scanning electron microscopy (SEM) of the carbon nitride films deposited on Si substrate at 830°C were consisted of hexagonal crystalline rods. The effect of substrate temperature on the formation of carbon nitrides was investigated. X-ray photoelectron spectroscopy (XPS) analysis indicated that the maximum value of the N/C atomic ratio in the films deposited at a substrate temperature of 830°C was 1.20, which is close to the stoichiometric value of C3N4. The X-ray diffraction (XRD) pattern of the film deposited at 830°C indicates no amorphous phase in the film, which is composed of β- and α-C3N4 phase containing an unidentified CN phase. Fourier transform infrared (FTIR) and Raman spectroscopy support the existence of CN covalent bond.