Characterization of structural and mechanical properties of DLC films deposited on the surface of minute-scale 3D objects: Changes in the incident behavior of carbon ions

Abstract

Diamond-like carbon (DLC) films have attracted great interest from the industry because they have beneficial mechanical properties such as low friction, high hardness, and wear resistance. DLC films have been used for the surface modification of various mechanical components, although many components that require surface treatments have complex three-dimensional (3D) surface structures. To date, 3D deposition of DLC films remains difficult using conventional methods. Particularly, uniform deposition technology on 3D components has not been developed for tetrahedral amorphous carbon (ta-C) films, which possess high CC sp3 bonds with high hardness. In this study, the filtered cathodic vacuum arc (FCVA) method was used to synthesize ta-C films on Si substrates placed on the sidewalls of trench-shaped and one-side tilted samples at various tilt angles and investigated their microstructure and hardness by Raman spectroscopy and nanoindentation. The results showed that the G peak position, full width at half maximum of G peak (FWHM (G)), and hardness of the ta-C film on the trench sidewall decreased as the depth from the top surface increased, similar to previous research. In contrast, ta-C films deposited on one-side tilted sample showed little depth dependence, and the film properties were determined by the tilt angle. We revealed that the film property dependence on the trench depth direction is due to the sputtered particles from the opposing trench sidewalls, resulting in graphitization of the film.