Tungsten oxide films were deposited on glass substrates (Corning #7059) and polycarbonate substrates by a pulsed laser deposition technique using the both targets WO3 and WO2. At this time, the difference in the transmittance, ΔT, between the annealed state and the as-deposited state of the films fabricated with WO2 target was about 70% at the wavelength of 400 nm and that of the films prepared with the WO3 target was about 60%. From XRD spectra and XPS spectra, it was found that the as-deposited state was an oxygen-deficient amorphous state and the crystalline state was caused by absorbing oxygen through the annealing process (at 500°C×10 min).
It was confirmed from the revolution-test of the disc structure that the values of CNR obtained at the write peak power 7.5∼9 mW was more than 50∼60 dB. From SEM images of top the view, it was presumed that a recording mechanism was related to a cooperative effect of the reflectivity change and the volume change induced in the recorded dot.