Annealing of nonhydrogenated amorphous carbon films prepared by filtered cathodic arc deposition

The effect of postdeposition annealing to 600 °C in vacuum on the hardness, modulus, film stress, and sp3 content of nonhydrogenated amorphous carbon was studied. The films were deposited using a filtered cathodic arc source and the film properties were varied by controlling the substrate bias. In films with an initial sp3 content of greater than 80% a significant decrease (from 10.5 GPa to less than 2 GPa) in the level of compressive stress was observed without deterioration of the mechanical properties. In films with an initial sp3 content of 50%, the stress and hardness remained constant. Films with lower sp3 content showed a significant increase in the level of stresses and only a marginal decrease in hardness. The evolution of stresses and hardness with annealing is discussed in light of a proposed microstructure of these amorphous films.