Analytical and functional characterization of ultrathin carbon coatings for future magnetic storage devices

Abstract

Ultrathin protective carbon coatings (5 nm) on top of magnetic hard disks deposited by filtered high current pulsed arc (HCA) were analyzed by various techniques. The films were compared to currently employed magnetron sputtered CN x overcoats in terms of functionality-determining film properties. X-Ray reflectivity (XRR) was used to determine film thicknesses and has been proved to be accurately applicable to carbon coatings down to ∼1 nm thickness. Time of flight-secondary ion mass spectrometry (ToF-SIMS) sputter depth profiling has proved similar carbon penetration depths into the unerlying magnetic media, both for HCA deposition and magnetron sputtering (MS), in spite of considerably higher deposition energies occurring during the HCA process. This fact suggests no negative impact on the macroscopic magnetic properties due to HCA deposition. The minimum thicknesses for full coverage of the media were evaluated by applying X-ray photoelectron spectroscopy (XPS) to the different film types. The results show a coverage limit of ∼1.0 nm for HCA coatings in contrast to ∼2.0–3.0 nm for CN x coatings indicating a significantly improved corrosion performance for overcoat thicknesses below 3 nm. Characterization with an AFM-based Nanoscratching technique suggests a more than two times increased resistivity against plastic deformation for HCA films compared to magnetron sputtered CN x overcoats.