Diamond-like carbon for magnetic storage disks

Diamond-like carbon films form a critical protective layer on magnetic hard disks and their reading heads. The ultimate limit to storage density is the super-paramagnetic limit, where the thermal energy is able to overcome the coercive energy of the magnetic bit. Perpendicular recording should allow storage densities up to ∼1 Tbit/inch2. This requires the read head to approach closer to the magnetic layer and ever-thinner layers of carbon 1–2 nm thick. A critical review of the properties of the main classes of carbon films used for magnetic storage disks is presented. Tetrahedral amorphous carbon can provide the atomic smoothness, continuity and density required for magnetic storage applications down to a few atomic layers thickness. The main approaches to assess the structural and morphological properties of ultra-thin carbon layers are reviewed. Raman spectroscopy, X-ray reflectivity, atomic force microscopy and surface acoustic waves based methods allow a full non-destructive characterization of ultra-thin carbon layers.