Synthesis of ultrathin carbon films by direct current filtered cathodic vacuum arc

Filtered cathodic vacuum arc was used to synthesize ultrathin carbon films on silicon substrates. The depth profiles, near-surface chemical composition, fractions of tetrahedral (sp3) and trigonal (sp2) carbon atom hybridizations, roughness, and hardness of the carbon films were determined from Monte Carlo (T-DYN) simulations and x-ray reflectivity (XRR), x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and surface force microscopy (SFM) measurements, respectively. Films of thickness of only a few nanometers possessed smaller sp3 fractions than much thicker films. The effective hardness was found to depend on the sp3 fraction and silicon-carbon composition profile. The formation of different carbon atom bonds, film growth mechanisms, and optimum process conditions for synthesizing ultrathin carbon films are interpreted in the context of T-DYN, XRR, XPS, AFM, and SFM results and surface bombardment, adsorption, and diffusion mechanisms.