Synthesis and characterization of C3N4 crystalline films on silicon

We report the successful experimental synthesis of nearly pure crystalline beta- and alpha-C3N4 films on a Si(100) substrate by bias-assisted hot-filament chemical vapour deposition. Scanning electron microscopy shows that the substrate surface is covered by polycrystalline C3N4 clusters 1-2 mu m in size with a density of 10(6)-10(7) cm(-2). Relative N/C compositions in the range 1.34-2.5 were obtained by energy-dispersive x-ray analysis. The lattice parameters a = 7.06 Angstrom and c = 2.72 Angstrom for beta-C3N4, and a = 6.48 Angstrom and c = 4.71 Angstrom for alpha-C3N4 were determined both by x-ray diffraction and by transmission electron microscopy. A buffer layer of C3-xSixNy was found.