Crystallization of amorphous carbon thin films in the presence of magnetic media

Amorphous carbon thin films, which are often used as protective coatings for magnetic hard disks, were deposited in a carbon/cobalt alloy/carbon trilayers (20/10/20 nm) and subjected to thermal annealing and cooling. The associated microstructural changes were analyzed by in situ transmission electron microscopy (TEM). TEM micrographs show that the amorphous carbon in contact with the magnetic media increases in graphitic content at annealing temperatures near 400 °C. It fully crystallizes between 500 and 600 °C. The microstructural changes at these temperatures suggest that the metals of the magnetic layers mediate graphitization, similar to the behavior of other eutectic metal metalloid systems (e.g., Al–Si, Ag–Ge). Calorimetric and magnetic measurements are consistent with a graphitization mechanism that includes a diffusional process. This article presents the experiments and proposes a graphitization mechanism.