Precursor gas effect on the mechanical and optical properties of ion beam deposited diamond-like carbon films

The effect of precursor gases on the diamond-like carbon (DLC) film deposition was investigated by the direct ion beam deposition method. DLC films were deposited using methane and benzene as the precursor gases. Ion energies for the deposition range from 100 to 700 eV were achieved by adjusting the beam voltage. The residual stresses, refractive indices and optical band gaps were compared at the same ion energy. We observed significant differences in residual stress and optical properties between these films. As in r.f. plasma-assisted CVD, the residual stresses of the films deposited from benzene show a characteristic behaviour of lower ion energy deposition than those deposited from methane. The present observations are discussed in terms of the difference in ion energy per carbon atom at the growth surface. We also observed that the Ar addition effect on the residual stress is strongly dependent on the precursor gases.