Diamond-like carbon thin films prepared by ECR argon plasma assisted pulsed laser deposition

Diamond-like carbon films were prepared by pulsed laser ablation of graphite target in argon plasma produced from electron cyclotron resonance (ECR) microwave discharge and analyzed by Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The analysis shows that the films prepared with argon plasma assistance have different chemical structure compared with the films prepared in vacuum without plasma assistance. The structure of the films prepared with plasma assistance depends strongly on the bias voltages applied on the substrate. Surface morphology observation shows that the films prepared with argon plasma assistance have a smoother surface than the films prepared without plasma assistance. The re-sputtering of the growing film due to the bombardment of the plasma stream results in reduction of the deposition rate. The ablation plumes during film preparation with and without plasma assistance were examined through optical emission spectroscopy. In vacuum, emission lines from mono-atomic carbons and carbon ions dominate the plume emission. In argon plasma, the plume emission exhibits different behavior in its temporal and spatial evolution. It is initially dominated by strong lines from mono-atomic carbons and carbon ions and then evolves to consist mainly of emissions from C2 molecules superposed on a featureless continuum. It is also found that the emission intensity of the C2 molecules as well as the continuum varies with the bias voltages.