A new protective layer for the rewritable digital versatile disk (DVD) of high transfer rate has been developed. High erasability was achieved using a tantalum oxide (Ta
2O
5)-based material as a protective layer for the four-layer structured optical disks. It was confirmed that the tantalum oxide of high contact angle promoted the nucleus formation in the active layer of Ge
2Sb
2Te
5, leading to enhancement of erasability. This new protective layer proved to be promising in the use for next generation rewritable DVD of blue laser type.
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