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 me dium are investigated with a tester at the wavelength of 680 nm. The carrie r-to-noise (CNR) and erase ratio depend upon the thickness of the upper die lectric layer and disc structure of the phase-change media, CNR exceeds 50 dB when the thickness of the upper dielectric layer is 300 Angstrom-675 Ang strom and erase ratio is above 25 dB when the thickness of the upper dielec tric layer is either 300 Angstrom or 600 Angstrom-700 Angstrom. CNR is 50 d B when the Al layer is 500 Angstrom-880 Angstrom-thick and erase ratio is 2 5 dB when the Al layer is 500 Angstrom-650 Angstrom-thick. The results cann ot be explained by optical simulations. The erase ratio is sensitive to the thickness of the upper dielectric layer, which is in good agreement with t he results of thermal simulations. It is unfavorable for CNR and erase rati o when the reflective layer is below 400 Angstrom or above 700 Angstrom. Ho wever, some of the structures are useful for rewritable discs.