We investigated the microstructure of phase change optical disks subjected to various initialization conditions using transmission electron microscopy (TEM). The effects of initialization powers on the erase ratio of phase change optical disks and corresponding microstructure changes were also studied. It was found that the increase of initialization power enlarged the width of the recrystallization band formed in the recording media of the disk. A wide recrystallization band was effective for decreasing the residual signal level hence the erase ratio increased. Disk dynamic test and TEM study results also revealed the deterioration of carrier-to-noice ratio (CNR) characteristic and the increasing trend of erase ratio was reduced when a substantial amount of coarse grains appeared in the crystalline region. This elucidates the necessity for phase change optical disks to have good heat dissipation property in order to suppress the formation of coarse granular structures.

The effect of critical fluctuations in magnetisation near the Curie point and far from the phase transition on the sputtering yield of the magnetic materials Ni and Gd is examined. The inclusion of the spin configuration of the nearest atoms around an atom sputtered from a surface has been found to result in an increase of the target sputtering yield by about 1.5 times compared with the ferromagnetic state.

Tellurium was studied as a mask film in a thermally induced superresolution rewritable optical disk for detecting below-diffraction-limit marks. Mark trains of 0.15 µm could be retrieved with 9 dB in carrier-to-noise (CNR) using an optical system with the laser wavelength of 780 nm and an objective lens of 0.55 numerical aperture. Readout cyclability was examined and methods to further improve readout cyclability were proposed.

Exchange-coupled double-layered (ECDL) films were adopted to increase density of magnetically induced super-resolution (MSR) media by using center aperture detection scheme, and to improve sensitivity of switching field simultaneously. A carrier to noise ratio of 40 dB was obtained at 0.5 µ m recording marks produced by a switching field of 75 Oe. Temperature dependence of interface wall energy affects recording/playback characteristics of ECDL MSR disks considerably.

New erasable thermal phase-change superresolution (EPSR) disks composed of mask and recording layers can increase recording density by the detection of the below-diffraction-limited marks within the readout spot. The formation of the aperture and the readout signal on the EPSR disk were analyzed. The feasibility of optically designed EPSR disks was evaluated by thermal simulation. A carrier-to-noise ratio of 32 dB at a mark size of 0.4 mum, 8 dB higher than that of a conventional disk, was obtained by application of a pulse-read method to the EPSR disks at a wavelength of 780 nm and a numerical aperture of 0.55.