Tetsu Ohishi

New Erasable Optical Media Using Sb-Se-Bi Alloy Film

Antimony-Selenium alloy film with Bismuth has good characteristics for erasable optical disk media. The mechanism of the reversible change is phase transition between amorphous and crystalline states. It is confirmed by small-angle X-ray diffraction analysis that Se-Bi component plays an important role in this reversible change. The minimum erase time is 1 μs. The film has high transition temperature and activation energy of crystallization. It has a long life span of written spots in amorphous state. Recording film of Sb-Se-Bi alloy is formed on 20 cm 0 PMMA substrate and is covered with protective films. The disk samples are written and erased at a speed of 1800 rpm, using an optical head with two diode laser beams. Carrier-to-Noise ratio is more than 55 dB at 5 MHz, 30 KHz bandwidth. The newly developed disk realized high performance and durability for the use of an erasable video file system.

RECORDING MECHANISM OF HIGH CN RATIO Sb-Se/Bi WRITE-ONCE OPTICAL DISC

Sb-Se/Bi films for write-once optical disks have been investigated and it was determined that the recording mechanism of Sb-Se/Bi film was interdiffusion and crystallization. Interdiffusion occurred below 200 C and Bi- Se crystals were produced within the interdiffused Sb-Se-Bi alloy layer. The peak concentration of Bi and Sb were exchanged between the as-deposited and after-annealed state. Sb-Sei films have a remaricably fast recording time of 30 ns at 9.7 mW laser power with a high CN ratio of over 60 dB at 8 MHz recording frequency. According to the Arrhenius equation, media life is presumed to be about 159 years at 25 C.