Synthesis and characterisation of carbon nitride thin films

Theoretical studies of β-C₃N₄ and other crystalline carbon nitride structures indicate that several crystalline phases are metastable, with high bulk modulus values. There are many reports of successful synthesis of some crystalline carbon nitride phases. In spite of questionable data analysis in a significant number of such reports, there is sufficient evidence in the literature to indicate that some nanocrystalline carbon nitride phases have been synthesised. Usually, such crystalline phases are embedded in an amorphous carbon nitride matrix. Amorphous carbon nitride films can be synthesised readily using many different techniques and are dominated by sp² carbon bonding, along with strong evidence of carbon-nitrogen bonding. Above a certain deposition temperature, fullerene-like structures can be formed with high hardness and excellent elastic recovery in nanoindentation testing. These thin films display excellent wear performance compared with carbon and hydrogenated carbon films under a wide range of tribological conditions. They are now widely used as protective overcoats in computer disk drive systems. In conclusion, several potential areas for future research in carbon nitride are suggested.