Diamond-like carbon (DLC) films were prepared on magnetic disk surfaces using an electron cyclotron resonance assisted microwave plasma chemical vapor deposition (ECR-MPCVD) system with variable radio-frequency (r.f.) substrate bias. Surface roughness of DLC deposited on hard disks was investigated by atomic force microscopy (AFM), which revealed that the DLC coated surfaces are smoother than those of the uncoated disks. Nitrogen incorporation into the films (a-C:N) further reduced the root-mean-square (RR IS) roughness to 2.5 Angstrom for films prepared at a substrate bias of - 120 V. Scratch resistance was improved when the DLC coatings were deposited at bias voltages greater than -90 V. However, the nitrogen introduction into the films deteriorated their scratch resistance. When the DLC films were subjected to an accelerated corrosive environment, pinhole density remarkably varied with the deposition conditions. The DLC films deposited with lower substrate biases and nitrogen incorporation resulted in poorer corrosion resistance. Internal stress, hydrogen content and graphitic cluster size of these films were correlated with data acquired by Raman analysis.