Ion-assisted pulsed magnetron sputtering deposition of ta-C films

The process of ion-assisted deposition of ta-C films by pulsed magnetron sputtering of a graphite target has been investigated. Probe measurements of the magnetron discharge plasma have been performed and its space- and time-dependent characteristics have been obtained as functions of the sputtering parameters and the bias voltage applied to the substrate. It has been shown that the density of the pulsed magnetron discharge plasma approaches values typical of pulsed laser or vacuum arc cathode sputtering of graphite (1017−1018 m−3). Raman scattering was used to examine the ta-C films produced at both low and high pulsed bias voltages applied to the substrate (Usub<1 kV, τ=160 s and 1 kV<Usub<6 kV, τ=40 μs, respectively). It has been shown that in the first case the maximum content of diamond-like carbon in the coating (50–60%) is achieved at a lower energy per deposited carbon atom (EC=100–300 eV) than in the second one (40–50% at EC=1100–1200 eV). Despite the lower diamond-like phase content in the coatings produced at a high bias voltage, they show better adhesion to the substrate due to the ion mixing between the film and the substrate and between the film layers. The use of shorter bias pulses is also important to prevent breakdowns of the deposited dielectric ta-C film.