Wen-Yih Liao

The Effect of Disc Structure on the Characteristics of the Phase-Change Medium

The effects of disc structure on the characteristics of the phase-change medium are investigated with a tester at the wavelength of 680 nm. The carrier-to-noise (CNR) and erase ratio depend upon the thickness of the upper dielectric layer and disc structure of the phase-change media. CNR exceeds 50 dB when the thickness of the upper dielectric layer is 300 A–675 A and erase ratio is above 25 dB when the thickness of the upper dielectric layer is either 300 A or 600 A–700 A. CNR is 50 dB when the Al layer is 500 A–880 A-thick and erase ratio is 25 dB when the Al layer is 500 A–650 A-thick. The results cannot be explained by optical simulations. The erase ratio is sensitive to the thickness of the upper dielectric layer, which is in good agreement with the results of thermal simulations. It is unfavorable for CNR and erase ratio when the reflective layer is below 400 A or above 700 A. However, some of the structures are useful for rewritable discs.