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A nickel(II) hydrazone complex was synthesized in order to obtain a suitable optical recording medium for the new
generation recordable blu-ray disk. Smooth thin films of the nickel(II) hydrazone complex were prepared by using the
spin-coating method. Absorption and reflectance spectra of the thin films were evaluated in the wavelength 300-700 nm.
Thermal properties of the nickel(II) complex were investigated by thermogravimetry (TG) and differential scanning
calorimetry (DSC). Optical constants (complex refractive indices N=n+ik) and thickness of the thin film, prepared on
single-crystal silicon substrate, were investigated on a rotating analyzer-polarizer scanning ellipsometer in the
wavelength 285-705 nm. In addition, in order to examine its possible use as a blu-ray recording medium, the spin-coated
film of the nickel(II) complex was prepared on K9 glass substrate with a silver reflective layer, and was studied by static
optical recording testing system with a 406.7 nm laser. It is found that the absorption spectra of the thin film has an
strong absorption band in the wavelength region 360-420 nm and a moderate absorbance at the 405 nm side, which
indicates that the absorption of the film is well matched with the laser wavelength of the 405 nm. The reflectance spectra
show that a high reflectivity of the thin film at 405 nm wavelength can be obtained by an optimum film thickness and an
appropriate metal reflective layer. The thin film of the nickel(II) complex gives a high n value of 1.62 and a low k value
of 0.33, corresponding to the wavelength of the blue laser of 405 nm. Measurements of the thermal properties show that
the nickel(II) complex holds a high thermal stability (~ 300 °C) and a sharp weight loss which are helpful to fabricate a
small and sharp recording mark edge. The results of the static optical recording test, using the nickel(II) complex thin
film as the recording layer, demonstrate that high reflectivity contrast (>50 %) can be obtained at an optimum laser
writing power and pulse width. In addition, the recording marks are durable even after 20000 times readout. These
preliminary results indicate that the nickel(II) hydrazone complex has great potential application for high-density discrecordable
system at wavelength of the 405 nm.
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