National Institute of Advanced Industrial Science and Technology

James Paul Fons

Junji Tominaga

Alexander Kolobov

Takayuki Shima

Yuzo Yamakawa

Recording and erasing of data in PRAM have hitherto been performed based on a change in physical characteristics caused by primary phase-transformation of a crystalline state and an amorphous state of a chalcogen compound including Te which serves as a recording material. Since, however, a recording thin film is formed of a polycrystal but not a single crystal, a variation in resistance values occurs and a change in volume caused upon phase-transition has placed a limit on the number of times of readout of the record. In one embodiment, the above problem is solved by preparing a solid memory having a superlattice structure with a thin film containing Sb and a thin film containing Te. The solid memory can realize the number of times of repeated recording and erasing of 10.

Solid memory

Recording and erasing of data in PRAM have hitherto been performed based on a change in physical characteristics caused by primary phase-transformation of a crystalline state and an amorphous state of a chalcogen compound including Te which serves as a recording material. Since, however, a recording thin film is formed of a polycrystal but not a single crystal, a variation in resistance values occurs and a change in volume caused upon phase-transition has placed a limit on the number of times of readout of record. In one embodiment, the above problem is solved by preparing a solid memory having a superlattice structure of thin films including Ge and thin films including Sb. The solid memory can realize the number of times of repeated recording and erasing of 10.

An object of the invention is to write-once record and reproduce, or only reproduce, a mark smaller than the resolution limit; obtain a high level of reproduction performance (CNR and the like); and realize a high level of reproduction durability. In the invention, between a signal reproducing functional layer composed of Sb or Te and a protecting layer there is introduced a thermally stable diffusion preventing layer, and thereby reactions between the signal reproducing functional layer and the protecting layer due to increased temperature can be prevented or suppressed while increasing reproduction durability.

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Tsukuba, Japan

James Paul Fons