Effect of ZnS Adhesion Layer on Overwrite Cyclability of Phase Change Optical Recording Media

A high-performance phase change optical recording disk, which has a five-layered structure, was proposed. This disk has a ZnS adhesion layer between a GeSbTe recording layer and a ZnS–SiO 2 second dielectric layer. A 2×10 5 overwrite cyclability was achieved with the original five-layered phase change optical recording disk. The cross-sectional transmission electron microscope observation and the in-plane X-ray diffraction measurement indicate that both the five-layered disk and the four-layered disk have almost the same crystalline structure. The contact angle measurements, however, indicate that the ZnS adhesion layer improves the adhesive force between the GeSbTe recording layer and the ZnS–SiO 2 second dielectric layer. It is considered that the high overwrite cyclability results from this improvement of the adhesive force. Moreover, the electron probe microanalysis results indicate that the ZnS layer acts as a protective layer against the Ge diffusion from the GeSbTe recording layer.