A brief review is described on the material characterization and application of the Ge(Sb70Te30) + Sb alloy. A mechanism to enable fast crystalline growth is discussed based on its single phase, hexagonal crystalline structure. A competitive process of amorphization and re- crystallization during re-solidification is discussed with a simple simulation model, where it is suggested that continuous crystalline growth from the boundary of molten area assures no resolution limit in the formation of amorphous mark edge. Two important concepts of 'enhanced re- crystallization' and '2T-period divided pulse strategy' are proposed to fully utilize this class of material. The enhanced re-crystallization realizes precise amorphous mark size control, realizing high density multi-level recording. The 2T-period divided pulse strategy resolves a pre-mature amorphization issue due to an insufficient cooling period in the case of over 100MHz clock frequency for high speed recording. Finally, it is reported that 120 Mbps digital video recording and over 40GB multi-level recording on CD size single layer are feasible.
MultiLevel recording for high-density, blue-laser systems has achieved approximately 5 X 10-5 BER before ECC using growth-dominant phase-change materials on a 0.6mm cover-layer, 405nm-wavelength, 0.65-NA system.
High speed overwriting capability of the nucleation-free and growth-dominant eutectic Ge(Sb<SUB>70</SUB>Te<SUB>30</SUB>)+Sb phase- change material, and its application to high speed overwritable DVD and CD, are discussed. The addition of Ge to Sb<SUB>70</SUB>Te<SUB>30</SUB>+Sb binary system could effectively suppress the nucleation in recrystallization process, while high Sb/Te ratio could realize a selective enhancement of crystalline growth-speed initiated from the boundary of an amorphous mark and its crystalline background. This resolved a trade-off in high speed erasure and archival stability of amorphous marks. Highly enhanced crystalline growth also caused serious recrystallization during amorphous mark formation, resulting in shrinkage of amorphous mark size (premature cooling issue). This premature cooling issue as well as premature heating issue, in multiple pulse strategy with such a short writing and cooling pulse as below 10 nsec at high clock frequency of > 100 MHz for over 4X speed rewritable DVD, were resolved with a 2T-period based multiple pulse strategy. Thus, feasibility of 2 - 4.8X CAV operatable rewritable DVD and 16X CD-RW was demonstrated.
Conference Committee Involvement (2)
Optical Data Storage Topical Meeting 2004
18 April 2004 | Monterey, California, United States