High-speed rewritable DVD up to 20 m/s with nucleation-free eutectic phase-change material of Ge(Sb70Te30)+Sb
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High speed overwriting capability of the nucleation-free and growth-dominant eutectic Ge(Sb70Te30)+Sb phase- change material, and its application to high speed overwritable DVD and CD, are discussed. The addition of Ge to Sb70Te30+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.