High performance phase change optical recording disk has been developed by using an oxygen-doped Ge–Sb–Te recording layer. The 5×105 overwrite cycles were achieved with this 6 at. % oxygen-doped phase change optical recording disk. The transmission electron microscope observation shows that the crystal grain size was enlarged and the “self-sharpening effect” disappeared with increasing of oxygen concentration. It is thought that the oxygen doping made it easy to grow the uniform large grain size without the self-sharpening effect around the amorphous mark and therefore, the overwrite cyclability of the phase change optical recording disk was improved.

The structural phase transition of ?-Fe precipitates in a Cu matrix is studied using the x-ray diffraction technique. At low temperature, the FCC lattice uniformly contracts along the c axis by 0.17%. In the c plane the mean value of the lattice spacing expands by 0.19%, but the atomic positions are modulated by a sinusoidal wave propagating along the [ l 1 01 direction with the (1 i 0) polarisation vector. Various properties of the periodic lattice wave (PLW) are studied. The wavelength and amplitude of the PLW depend on the size of the precipitates. The origins of the PLW and the size effects are discussed.

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