Diamondlike carbon films by rf plasma-assisted chemical vapor deposition from acetylene

This paper is an overview of studies performed at the IBM Thomas J. Watson Research Center on diamondlike carbon (hydrogenated amorphous carbon) films, including some recent results on their tribological properties. The films were prepared by rf plasma-assisted chemical vapor deposition (PACVD) from acetylene. Their structure and composition were characterized by a variety of methods such as X-ray and TEM diffractometry, XPS, high-resolution
¹³
C NMR spectroscopy, and H(
¹⁵
Nα,γ)C nuclear-reaction profiling. Their adhesion to various substrates, coefficients of static and dynamic friction, and wear resistance were also characterized. It was found that the films were essentially amorphous, reaching their bulk composition after 40 nm of growth above the initial growth interface. Their bulk composition included about 40% hydrogen. More diamondlike carbon bonding was obtained at the initial growth interface than in the bulk range. The ratio of sp
²
to sp
³
carbon atoms was found to be 1.6, with virtually all sp
³
carbon atoms bound to one or more hydrogen atoms. The diamondlike carbon films (DLC) displayed excellent adhesion to the surface of Si. Furthermore, the films could be bonded to films of otherwise nonbonding metals, provided the metals formed stable silicides. By using an interfacial Si film several atomic layers thick, adhesion to the metal films could be improved to the extent that attempts to detach the DLC films fractured the underlying metal films. The adhesive DLC films were found to have a very high resistance to sliding wear and chemical attack, and are therefore useful in various applications as very thin protective coatings.