Bert Scheffel, Stefan Saager, Ludwig Decker, Olaf Zywitzki, Fraunhofer Institute for Electron Beam and Plasma Technology FEP; Dresden, Germany
The anodic arc evaporation process, combined with a hollow cathode arc discharge, is an intensive plasma deposition technique that has been employed to deposit hydrogen-free carbon films through graphite evaporation. These films have demonstrated exceptional hardness, characterized through nanoindentation, Raman spectroscopy, FE-SEM, AFM, and spectroscopic ellipsometry. The relationships between process parameters, such as substrate temperature and deposition rate, and the properties of the films are discussed. Films deposited at substrate temperatures below 200°C exhibit high hardness (61-83 GPa) and a significant Young's modulus (588-860 GPa). Raman spectra indicate a notable presence of tetrahedral sp3 bonds, ranging from 70% to 88%. The coatings are remarkably smooth and free of droplets, as confirmed by FE-SEM and AFM analysis. Exceptionally high deposition rates of 4-18 nm/s make these tetrahedral amorphous carbon (ta-C) coatings a promising choice for industrial applications. The ta-C coatings' combination of high hardness and smooth surface characteristics renders them ideal for use as wear-resistant coatings.