Abstract
The deformation of polycarbonate substrate during direct-overwriting (DOW) process of phase-change (PC) optical disc with germanium nitride (Ge-N) interface layers was studied. From scanning probe microscopy (SPM) results, the deformation of the land/groove caused by thermal energy during the writing process was highly reduced by the Ge-N interface layers. The Ge-N interface layers not only prevent sulfur atom diffusion into the PC layer during DOW, but also protect the substrate from thermal damage. Therefore, the optical disc with Ge-N interface layers achieved DOW cycles 2 orders higher than that of the conventional rewritable disc. The substrate deformation lifetime during the DOW process was multiplied by approximately 100 times.