With increasing demands made on the performance of ultra-thin (<3 nm) overcoats in magnetic recording media, novel deposition approaches are needed to produce films that are mechanically robust and provide corrosion resistance to the underlying media. We have used the ECR (electron cyclotron resonance) approach to create a high-density plasma and have controlled the ion energy via the bias to increase the atomic mobility and density of deposited films. Using this approach, we have deposited a series of a-C:H (N) films with thicknesses as small as 0.8 nm and correlate their corrosion, wear, and nanometer-scale scratch resistance performance with film density measurements. We also present findings that the interaction with the cobalt underlayer changes with the ECR approach. The oxidation state of the cobalt underlayer was investigated by high resolution ESCA and preliminary results showed that the percentage of cobalt oxide was significantly decreased by the ECR approach while the C (1s) spectra showed the formation of cobalt carbide at the interface. We will contrast the behavior of films deposited with this approach with those conventional sputtered a-C:H (N) films, and comment on the extendibility of traditional overcoat designs.