Synthesis and properties of carbon nitride thin films

The objectives of the present research were to synthesize a new class of superhard and/or super wear-resistant carbon nitride thin films and to characterize them in terms of composition, structure, chemical bonding, hardness, and tribological properties. Amorphous carbon nitride (CN{dollar}rm sb{lcub}x{rcub}){dollar} thin films and crystalline CN{dollar}rm sb{lcub}x{rcub}/{dollar}TiN composite thin films have been synthesized using unbalanced magnetron sputtering techniques. An ionized magnetron sputtering system was also constructed to produce CN{dollar}rm sb{lcub}x{rcub}{dollar} films.; The N/C ratios of smooth CN{dollar}rm sb{lcub}x{rcub}{dollar} thin films range from 0 to 0.5 depending on deposition conditions. C and N are primarily sp{dollar}sp2{dollar} bonded. The hardness of CN{dollar}rm sb{lcub}x{rcub}{dollar} films is strongly dependent on nitrogen partial pressure and substrate pulse bias. A maximum hardness of 25 GPa was reproducibly achieved under the optimum deposition conditions. Block-on-ring tribotesting demonstrated that CN{dollar}rm sb{lcub}x{rcub}{dollar} coatings exhibit relatively low dry friction coefficient {dollar}(sim{dollar}0.1). CN{dollar}rm sb{lcub}x{rcub}{dollar}-coated M2 steel sample shows superior wear-resistance compared to those coated with amorphous carbon, TiN, and NbN under dry sliding tests against 52100 steels in air.; The addition of an rf coil in the ionized magnetron sputtering system clearly increases the ion current density. However, film hardness is not significantly different from that obtained by conventional magnetron sputtering methods. Typical N/C ratios obtained from films prepared under a variety of conditions with the rf-induced plasma stay at {dollar}sim{dollar}0.3-0.4, similar to those obtained without the rf plasma.; There is no evidence of the formation of crystalline {dollar}beta{dollar}-{dollar}rm Csb3Nsb4{dollar} in the CN{dollar}rm sb{lcub}x{rcub}{dollar} films prepared so far. However, fully crystalline CN{dollar}sb{lcub}rm x{rcub}{dollar}/TiN multilayer composite coatings have been synthesized with nanoindentation hardness in the range of 45-55 GPa. TEM studies found that the CN{dollar}rm sb{lcub}x{rcub}{dollar}/TiN coatings were fully crystalline and dense at small bilayer thicknesses. An amorphous phase was formed when the CN{dollar}rm sb{lcub}x{rcub}{dollar} layer thickness exceeded 4-5 nm. The coating hardness was found to be strongly dependent on processing parameters. Ion bombardment on growing film by applying a substrate bias is crucial for achieving dense coatings with high hardness.