Physical properties of diamondlike carbon films deposited in mixed atmospheres of C₂H₄–Ar, C₂H₄–H₂, and C₂H₄–N₂

Diamondlike carbon films were deposited in a pure C₂H₄ atmosphere and in mixed atmospheres of C₂H₄–Ar, C₂H₄–H₂, and C₂H₄–N₂ by radio frequency plasma chemical vapor deposition. The partial pressures of Ar, H₂, and N₂ were 25%, 50%, and 66.7%, respectively. The films were deposited with a high negative bias of −610 V. The hardness, the density, and the internal stress of the films decrease and the amount of gas evolution increases with increasing partial pressures of N₂ and H₂, while they do not depend on the partial pressure of Ar. These results show that N₂ and H₂ react with carbon in the films and decrease the degree of the crosslinking in the network structure, while Ar does not change the degree of crosslinking. The surface is very flat and the roughness (R_max) is below 1 nm. The hardness is 40 GPa for the films deposited in atmospheres of pure C₂H₄ and mixed C₂H₄–Ar with a bias of −610 V.