Wettability, nanoscratch resistance and thermal stability of filtered cathodic vacuum arc grown nitrogenated amorphous carbon films

• Increase in N content increases the stability of CN bonds (4 to 18% for 8 to 17% N).
• Polar surface energy increases by nitrogen content (10 to 22 mJ/cm2 for 0 to 16% N).
• a-C:N deposited at 0 & 100 V bias has higher thermal stability compared to 200 & 300 V deposited films.

Composition, structure, surface energy, nanoscratch resistance and thermal stability of nitrogenated amorphous carbon films grown by filtered cathodic vacuum arc (FCVA) are studied in this paper. X-ray photoelectron spectroscopy and electron energy loss spectroscopy studies reveal that by controlling the nitrogen flow rate and substrate bias carbon films with different bonding structures and composition are formed. Higher nitrogen flow rate results in higher nitrogen content of the film and the stability of CN bonds. Increasing the nitrogen content of the films (0 to 16 at.%) increases the polar surface energy (10 to 22 mJ/m2) of the films while the dispersive surface energy does not change significantly. Thermal stability of the films strongly depends on the composition and bonding structure. The films deposited at higher substrate bias (300 V) and containing higher nitrogen content undergo graphitization at lower annealing temperatures. There is no significant difference in the scratch resistance of the films at small scratch loads (up to 35 μN). Further increase in the scratch load results in larger scratch depth in the film deposited at high nitrogen flow rate (40 sccm).