Coherent interlayer cross talk and stray-light intensity of multilayer read-only-memory (ROM) optical disks are investigated. From results of scalar diffraction analyses, we conclude that layer separations above 10 microm are preferred in a system using a 0.85 numerical aperture objective lens in terms of signal quality and stability in focusing control. Disk structures are optimized to prevent signal deterioration resulting from multiple reflections, and appropriate detectors are determined to maintain acceptable stray-light intensity. In the experiment, quadrilayer and octalayer high-density ROM disks are prepared by stacking UV-curable films onto polycarbonate substrates. Data-to-clock jitters of < or = 7% demonstrate the feasibility of multilayer disk storage up to 200 Gbytes.

The effective thermal conductivity was investigated for granular beds of various binary mixtures. Samples used were two or three sizes of glass beads, resin particles and copper spheres respectively. A unit cell model was developed after due consideration of particle diameter ratio and it was assumedthat the coordination numberwas a function of diameter ratio and volumefraction of components. Predicted values coincided with experimental ones, in which the ratio of diameters was 1-2.8 and the ratio of solid conductivities was 1-5.8, within 6 % deviation.

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A near-field optical technology using a solid immersion lens (SIL) has been actively studied to expand the storage capacity higher than 100 Gbytes per layer in a 12-cm-sized optical disk. However, the working distance of an objective lens in a near-field optical disk system should only be 25 nm or less. Therefore, from the practical viewpoint, a topcoat layer is required to protect the recording layer when the SIL collides with a disk surface because of disturbances such as dust, shock and vibration. From a mechanical viewpoint, the topcoat should have the mechanical toughness to protect the disk surface. Moreover, from an optical viewpoint, it should have refractive index higher than the numerical aperture of an SIL to achieve a sufficient evanescent couple between the SIL and disk surface. In this study, we describe a topcoat for a near-field optical recording. First, we investigate the topcoat performance from the optical viewpoint. Second, we evaluate the topcoat performance from a mechanical viewpoint. Finally, we report the results of recording experiments for a disk with the topcoat and discuss its performance.

A computer-aided method is developed for automatically correcting the slide distortions of torque curves measured with a non-zero torque magnetometer. This method is based on a previously obtained analytic expression of the first harmonic corresponding to the distorted calibration torque curve.

A band of disorder is observed following the annealing of surface amorphous layers produced by ion bombardment. The depth of the band's centre is just below the original amorphous/crystalline interface. The ion bombardment simulation computer program TRIM.CASCADE has been used in conjunction with ion channelling measurements to predict the areal density of atoms available for the formation of this band of disorder. The variation in the amounts of disorder expected due to changing the implantation parameters: ion dose, ion energy and implantation temperature are reported. The predictions are compared with the published transmission electron microscopy results and electrical measurements of other workers. The implications of this work for t h e technique of pre-amorphisation are also discussed.

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