Phase-change Optical Disk with Nitride Interface Layers

Abstract

Our DVD-RAM/2.6GB was just commercialized in this year. Today, our R/D activities are aimed toward the next generation of DVD-RAM media and even the generation beyond that. We are striving to achieve higher recording density, a higher data transfer rate and higher reliability (cyclability). Through our study, we have found that a nitride interface layer was very effective for increasing the performance of phase-change optical disks. In this paper, we will present a new disk structure having Ge-N layers at the interface between the Ge-Sb-Te active layer and the ZnS-SiO2 protective layers. The effects of the nitride layer and the disk performance will also be described.

Method and physical mechanism of initialization-free phase-change optical recording

“…The crystallization kinetics of PC recording media is not only determined by the composition and film thickness of the PC recording layer, but is also significantly influenced by the disk structure and the materials of other layers in the disk, especially the layers (interface layer or dielectric layers) near the PC recording layer. For example, GeN interface layers, which sandwich the PC recording layer, not only lead to a significant improvement in overwrite cyclability because they can restrain sulfur atom diffusion from the dielectric layer to the PC recording layer, but they also accelerate the crystallization process of PC media [17]. Therefore, the material and crystallization properties of the nearby layers are very critical and useful for the crystallization of the PC recording layer.…”

Analysis of the Degradation Mechanism during Repeated Overwrite of Phase-Change Discs

“…The problem has been tackled in various ways. For instance, Yamada et al 1,2) and Miao et al 3) applied a thin caplayer of GeN at one or both sides of the phase-change layer, preventing S atoms from the ZnS:SiO 2 layer to diffuse into the phase-change layer. Or in the opposite direction: Ebina et al 4) applied a ZnS caplayer, which has been measured to prevent Ge from diffusing out of GeSbTe layer, a property that they held responsible for the improved overwrite cyclability.…”

Effect of Dielectric Material Films on Crystallization Characteristics of Ge2Sb2Te5 Phase-Change Memory Film

“…As mentioned above, the erasing characteristics of phasechange optical disks proved to be markedly enhanced by providing a dielectric film directly on the phase-change film. 8) This fact suggests that a crystallization speed of a phase-change film is accelerated by the presence of a dielectric film; however, it has not yet been clarified whether this effect is due to differences in crystallization temperature caused by its contrasting activation energy, or whether it is simply the stable composition of the dielectric film that prevents it from mixing with the phase-change film.…”