Effect of chamber pressure and hydrogen on the formation of C3N4 films deposited on quartz substrates via MPCVD

Carbon nitride (C3N4) films were deposited on quartz substrates via microwave plasma chemical vapor deposition. C3N4 films were synthesized under different chamber pressures with and without hydrogen. X-ray diffraction (XRD) revealed films with better α-C3N4 and β-C3N4 structures above 90 Torr chamber pressure with hydrogen condition. When the chamber pressure increases, the C3N4 crystal phase is stronger and more conspicuous. Scanning electron microscopy (SEM) shows the surface morphology of C3N4 films exhibiting the hexagonal rod structure. Low chamber pressure resulted in small grains, while higher pressures resulted in large grains. The C3N4 grains were about 10–12 μm in length and 6–8 μm in width under 100 Torr chamber pressure and hydrogen condition. The center line average roughness from atomic force microscopy (AFM) images showed that the average roughness with hydrogen was higher than that without hydrogen. Fourier transform infrared (FT-IR) spectroscopy confirmed that all the C3N4 films contained C–N bonds. The hardness of C3N4 films measured using a nanoindenter with hydrogen condition was higher than that without hydrogen.