Deposition and characterization of carbon nitride films from hexamethylenetetramine/N2 by microwave plasma-enhanced chemical vapor deposition

Carbon nitride thin films were deposited on Si(1 0 0) substrate by microwave plasma-enhanced chemical vapor deposition (PECVD). Hexamethylenetetramine (HMTA) was used as carbon and nitrogen source while N2 gas was used as both nitrogen source and carrier gas. The sp3-bonded C–N structure in HMTA was considered significantly in the precursor selection. X-ray diffraction analysis indicated that the film was a mixture of crystalline a- and b-C3N4 as well as graphitic-C3N4 and b-Si3N4 which were not easily distinguished. Raman spectroscopy also suggested the existence of a- and b-C3N4 in the films. X-ray photoelectron spectroscopy study indicated the presence of sp2- and sp3-bonded C–N structures in the films while sp3C–N bonding structure predominated to the sp2 C–N bonding structure in the bulk composition of the films. N was also found to be bound to Si atoms in the films. The product was, therefore, described as CNx:Si, where x depends on the film depth, with some evidences of crystalline C3N4 formation.