Structure and mechanical properties of hard amorphous carbon-nitrogen films obtained by plasma decomposition of methane-ammonia mixtures

Abstract

Hard amorphous hydrogenated carbon-nitrogen films (a-C(N):H) were deposited by rf plasma decomposition of methane-ammonia mixtures onto silicon substrates. The incorporation of nitrogen increases with the partial pressure of ammonia. On the other hand, the deposition rate decreases. The samples were characterized by a a combination of analytical techniques: MeV ion beam techniques (RBS,NRA and ERDA), SIMS, AFM, EELS, infrared absorption and Raman spectroscopy. The Vickers hardness and the internal stress of the films were also determined. Infrared results indicate that the nitrogen is incorporated into the amorphous network mainly as terminating groups at the expense of C-H radicals. EELS and Raman results show that the incorporation of nitrogen induces a progressive graphitization of the films. The incorporation of up to 11 at% nitrogen reduces the internal stress of the films by a factor of two without significant modification of the film hardness.