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Media Technologies of 20 GB Single-Layer Rewritable Phase-Change Disc for HD DVD System

Sufficient signal amplitude, erase ratio and low amount of cross-erase must be attained to achieve higher recording capacity of rewritable phase-change media. We have developed new media technologies, such as the GeTe-rich GeTe-Sb2Te3 pseudobinary alloy recording film partially substituted with bismuth and an additional layer to control thermal diffusion. The recording layer material enables a high erase ratio with a high signal amplitude. The additional layer also reduces the amount of cross-erase while maintaining a sufficient erase ratio. We have successfully demonstrated rewritable phase-change media having 20 GB capacity by using these media technologies for the HD DVD system with a blue-violet laser diode having the wavelength of 405 nm, a numerical aperture of the objective lens of 0.65 and light incident on a 0.6-mm-thick substrate. In this paper, we describe our new media technologies and the evaluation results, such as tilt margins, uniformity, overwriting cyclability and life durability.