Effect of methane concentration on the growth of crystalline C3N4 films

The effect of methane concentration on the growth of crystalline alpha- and beta-C3N4 films have been studied in bias-assisted hot filament chemical vapor deposition system by using a low-pressure methane-nitrogen gas mixture. Scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction have been used to characterize the films obtained. The results indicate that a methane concentration of 0.5 vol% leads to a compatible growth of alpha- and beta-C3N4; 1.0 and 2.0 vol% lead to the selected growth of beta-and alpha-C3N4, respectively. The lattice constants of the C3N4 phases synthesized at different methane concentrations coincide very well with the ab initio calculation results. Moreover, two recently identified C-N new phases with tetragonal and monoclinic structure are found in all of the depositions.