Effect of nitrogen concentrations on optical,structural and mechanical properties of self organized a-C:N films

Low friction and surface hardness has become an important aspect to study and understand surface engineering of diamond like coating. Investigation of structural and mechanical properties of nitrogenated amorphous Diamond Like Carbon coating has been done. The cross-sectional microstructures, elemental compositions and various phase constituent of the coated layers under different processing conditions have been characterized. Films are deposited in presence of 5%–20% with the increasing rate of 5% and 40% of N₂ partial pressure along with Ar gas. 20% N₂ pressure shows a critical behavior in Raman spectroscopy and XPS. In this condition the film shows more uniform coating with vertical growth structures as well as brittle behavior. The micro-structural changes on the surface due to migration of N₂ and its related surface properties have been examined. AFM studies clearly show that the percentage change in average roughness decreases to 17% as the film thickness increases at 20% N₂ incorporation. The positive changes in its mechanical properties have been observed by Nano-indentation techniques. Significance of DLC coating in this condition is clearly seen with the increasing sp³compositions by XPS analysis. All results have been correlated and hence critical range of nitrogen partial pressure has been observed between 20%-23% to give similar sp³ fraction and hence properties that of pure DLC films.