Deposition of ultra-thin diamond-like carbon protective coating on magnetic disks by electron cyclotron resonance plasma technique

Diamond-like carbon (DLC) films were prepared on Si and magnetic disks using an electron cyclotron resonance assisted microwave plasma chemical vapour deposition system with variable radio-frequency (rf) substrate bias. Surface morphology of disks deposited with 10 nm DLC was observed under atomic force microscopy (AFM), which revealed surfaces smoother than the uncoated disk. The root-mean-square roughness decreased with increasing substrate bias and reduced to 0.23 nm for film prepared at a bias of -150 V. Internal stress and hardness of the resulting films deposited on Si were investigated by curvature measurement and nano-indentation, respectively. Both internal stress and hardness increased with increasing ion energies. At a bias beyond -120 V, the film structure changed from diamond-like to graphite-like. There was also an improvement of scratch resistance of the DLC coatings deposited at bias >-90 V.