NITROGEN-INDUCED MODIFICATIONS IN MICROSTRUCTURE AND WEAR DURABILITY OF ULTRATHIN AMORPHOUS-CARBON FILMS

A systematic experimental investigation was carried out to understand the effects of nitrogenation on the microstructure and wear durability of thin amorphous-carbon films. The films were fabricated with 0%, 10 %, 15%, 20%, 30%, 40%, and 50% N-2 in the sputter gas. Microstructure properties were characterized using Rutherford backscattering spectros copy, electrical resistance, Raman spectroscopy, and x-ray photoelectr on spectroscopy. Nanohardness and scratch wear resistance of the films were studied with an atomic force microscope equipped with a diamond tip. The head-disk interface tribological properties of the films were tested with industrial standard contact-start-stop wear instrumentati on. The results indicate that the introduction of nitrogen into the ca rbon film increases the film lattice disorder and allows for the forma tion of carbon-nitrogen single, double, and triple bonds. The nitrogen atomic concentration in the film, electrical resistance, and the rati o of carbon-nitrogen bonds to carbon-carbon bonds increase with increa sing N-2 in the sputter gas. A significant addition in C=N bond percen tage is observed when the N-2 exceeds 30% in the sputter gas. Both the nanohardness and scratch wear resistance of the carbon film can be si gnificantly improved by incorporating an optimized nitrogen concentrat ion in the film. In this study, the film processed with 30% N-2 showed the highest nanohardness and wear resistance.,The degraded nanowear r esistance for the films processed with 40% and 50% N-2 is attributed t o the significant addition of C=N bonds. Within a wide process range ( 15%-30% N-2), the films exhibit excellent tribological performances at the head-disk interface. The wear mechanisms from the contact-start-s top wear tests are interpreted based on the understanding of film stru ctures and film mechanical properties. (C) 1998 American Institute of Physics.