High density rewritable recording and readout characteristics with a solid immersion lens (SIL)-based near-field
recording (NFR) are investigated. Substrates for high density are prepared using a phase transition mastering
technique. Cover-layers with different refractive index for different effective numerical apertures in the SIL optics
are coated on rewritable NFR discs for cover-layer incident near-field recording configuration. Two different
effective numerical apertures are chosen between 1.45 and 1.85 to cope with about 70 GB and more than 100 GB
per disc, respectively. The performance readout signals is investigated and compared in terms of increasing
recording densities with reducing track pitch.
Phase-change wet-etching technology using GeSbTe phase-change films are developed. Selective etching between an
amorphous and a crystalline phase can be carried out with an alkaline etchant of NaOH. The degree of etching was
investigated by optical images using an optical microscope and the transmittance between the crystalline and amorphous
films coated on transparent substrate during an etching process. Etching selectivity is dependent not only on the
concentration of the alkaline etchant but also on a film structure. Specifically, metal films for a heat control cause
marked effects on the etching properties of GeSbTe film. Surviving amorphous pits can be obtained with Al metal layer,
however etched amorphous pits are seen with Ag metal layer. An opposite selective etching behavior can be observed
between samples with two different metal layers.
KEYWORDS: Contamination, Near field, Near field optics, Head, Sputter deposition, Optical storage, Coating, Transmittance, Interfaces, Chemical species
Contamination at the head-disk interface (HDI) was observed for first-surface near-field recording (NFR) under accumulation over a long writing time with a high writing power. The contamination was caused by laboratory dust coupled with the heat from the focus of the writing laser at the HDI. One suggested solution to the problem is that a cover layer should be laminated for cover-layer-incident NFR. A uniform and edge-bead-free UV-curable cover layer was laminated by using an outer-ring technique. Diamondlike carbon films were optimized and coated on the cover layer, and then a lubricant film was applied to reduce the tribological problems at the HDI.
KEYWORDS: Interfaces, Tellurium, Crystals, Optical discs, Optical storage, Clocks, Digital video recorders, Germanium, Digital video discs, Multilayers
We have developed phase change optical media with appropriate write strategy for 1X-2X dual speed Blu-ray Disc system and for the future high speed phase change optical data storage. For recording layer, eutectic-based Ge(Sb70Te30)+Sb material was used and Sb/Te ratio and Ge content were optimized to obtain proper erasability and archival stability of recorded amorphous marks. The recording layer is wrapped up in GeN interface layers to obtain reasonable overwrite cyclability and higher crystallization speed. In addition, we designed appropriate write strategy so-called time-shifted multipulse(TSMP) where the starting positions of multipulse parts are shifted from reference clock. With this write strategy, the overall jitter characteristics of the disc was improved and especially we found that trailing edge jitter was improved much more than leading edge jitter. Thus feasibility of 1X-2X dual speed applicable Blu-ray Disc and its write strategy was demonstrated.
The needs of recording media for high density are increasing for huge data base and the digital TV environment in near future. A lot of technologies are developed and being developed to achieve a high recording density in MO media. It is a principal approach to circumvent the limit of the spot size of laser due to the diffraction.
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