No abstract

Transmission, replica, and scanning electron microscopy studies of the holes formed by laser irradiations on Cr/ AI, Si/ AI, and C/ Al bilayer films were carried out. For Cr/ Al and C/ Al films, well-shaped circular holes were formed independently of the thickness ratio. In the case ofSi/ Al film, circular holes were formed only when the thickness ratio of Si was small. The peripheral regions of holes had several types of swell. In Cr/ Al film there existed the steep swell at the hole edge and successively the gentle swell. The swells ofC/ Al film were rough in shape with thickness irregularities. Many thinned portions appeared in the swell of Si/ Al having large thickness ratio ofSi. The threshold power to form a hole was much lowered by coating the Al film with Cr, Si, or C, and the threshold value of 0.4 W for 60-nm-thick Al was reduced to about 0.04 W for 10 nm Cr/50 nm Al and 0.08 W for 20 nm Si/40 nm AI. The numerical analysis for temperature rise of the bilayer films was made using the finite difference method considering the phase transitions of the materials. The mechanisms of hole and swell formations in the bilayer films are also discussed.

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Following up the popularization of Compact Disc (CD), the epoch of digtial audio is coming really and truly. In the new period the actualization of an erasable optical disc system will be expected greatly.

We have developed a video disk recorder system using a magnetically induced super resolution (MSR) magneto-optical (MO) disk 120 mm in diameter and achieved a user data capacity of 4.1 Gbytes per disk using land/groove recording technology, a laser wavelength of 685 nm, and (1, 7) run-length limited (RLL) code. In this case, track pitch is 0.7 µm and minimum mark length is 0.4 µm. The system can record 125 minutes of moving images encoded using the MPEG2 method. In this paper we describe our high-density magneto-optical recording technology and the video disk recorder system which incorporates magnetic field modulation.