Shielded arc ion plating and structural characterization of amorphous carbon nitride thin films

Abstract

We synthesized amorphous carbon nitride films with shielded arc ion plating (SAIP), investigated the effects of deposition pressure and substrate bias on the structure of the films and analyzed chemical bonding states in the films. The films prepared consist mainly of sp 3 and sp 2 plain (graphite- and pyridine-like) microdomains. The N/C ratios of the films increased from 0.13 to 0.51 with rising pressure. There is a larger amount of the sp 2 plain microdomains over the sp 3 microdomains in the films and the films are soft despite the change in deposition pressure. On the other hand, applying proper bias voltages to substrates makes the films harden, while excessive ion bombardment decreases the film hardness. The hardening mechanism for the amorphous carbon nitride films is the same as that for conventional diamond-like carbon (DLC) films. The hardest carbon nitride film prepared at the optimum voltage of −300 V is twice as hard as a Si substrate. The effect of carbon network on the film hardness is much larger than the nitrogen concentration and the types of carbon-nitrogen bonds.