Structural and mechanical properties of Ti-containing diamond-like carbon films deposited by filtered cathodic vacuum arc

Titanium-containing diamond-like carbon films were deposited on silicon wafer substrates at room temperature by the filtered cathodic vacuum arc technique. A wide range of negative bias voltage from 0 to 500 V was applied to the substrates during film deposition. The structural and mechanical properties of the films were analysed by Rutherford backscattering spectroscopy, Raman spectroscopy, surface profilometry, the scratch test, and nanoindentation. For comparison, a set of pure diamond-like carbon films were also deposited and analysed. Raman spectra showed that all the samples had the lowest intensity ratio of the D peak to G peak (I_D/I_G) at a bias voltage of approximately 80 V, which normally represents the highest sp³-bonded carbon components in the films. Correspondingly, the highest internal stress (σ), hardness (H) and Young's modulus (Y), and the lowest scratch critical load (L_c) were observed at the bias voltage of approximately 80 V. With the increase of titanium content in the films, I_D/I_G increased, while σ, H, and Y reduced, and L_c increased. The results demonstrate that the addition of titanium into the diamond-like carbon films could significantly reduce the internal stress and, as a consequence, effectively improve the adhesion properties of these films.