Abstract
We carried out a feasibility study on rewritable phase-change optical disks with more than two recording layers. Dynamic recording-playing evaluations of the test disks and Tx measurements revealed the thinning limit of the examined GeSbTe memory film to be 2 nm. The disk with a 2.5-nm thick recording film showed a high transmittance of 77 % at a wavelength of 405 nm, and a CNR of 45 dB. Based on our experimental results, we conclude that at minimum, a quadruple-layer disk for blue lasers will be possible pending some improvements in the maximum output of laser diodes, the sensitivity of optical detectors and the crystallization speed of memory films.
