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Low Noise, Phase-Change Optical Recording Media

IP.com Disclosure Number: IPCOM000040801D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Chen, M: AUTHOR [+5]

Abstract

Crystals which fall into the cubic class are optically isotropic. Therefore, when a phase-change optical recording medium is chosen from materials which crystallize into cubic structures, there is no detectable noise due to grains, independent of the grain size. On disks made using materials which form cubic crystals, we were unable to detect any additional noise upon crystallization of a track. In contrast, on Te-alloy disks, which crystallize predominantly into anisotropic Te crystals, the disk noise increased by 5dB after crystallizing.

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Low Noise, Phase-Change Optical Recording Media

Crystals which fall into the cubic class are optically isotropic. Therefore, when a phase-change optical recording medium is chosen from materials which crystallize into cubic structures, there is no detectable noise due to grains, independent of the grain size. On disks made using materials which form cubic crystals, we were unable to detect any additional noise upon crystallization of a track. In contrast, on Te-alloy disks, which crystallize predominantly into anisotropic Te crystals, the disk noise increased by 5dB after crystallizing.

Optically isotropic crystals are not restricted to simple cubics. Besides the simple cubic structure, other cubic structures include face-centered cubic, body- centered cubic, diamond, zinc-blend, and wurzite. In addition to thermodynamically stable binary and ternary cubic crystals, there also exist metastable cubic crystals which are potential phase-change recording materials.

A simple corollary to the above idea is to choose materials, which are not cubic, but which are as optically isotropic as possible, to achieve some degree of grain noise immunity.

While the discussion here has been of phase-change optical recording materials, it is evident that the same idea has applicability towards crystalline magneto-optic materials.

Disclosed anonymously

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