Write compensation using the thermal transfer function in an optical disk.
The theoretical basis for a write-compensation scheme is developed with a simplified thermal transfer function in an optical disk. The thermal transfer function is analytically approximated to a first-order exponential filter similar to that of an integrating circuit. A write-compensation method is then given directly by the inverse function of the filter. A simplified form of the compensation is also derived, and this is verified by experiments. This method eliminates the thermal interference and shows how to form mark edges uniformly for an arbitrary optical disk.
Erasing Characteristics and Crystallization Process of GeSbTe Phase-Change Optical Disk Media at Very Fast Linear Velocities
The erasing characteristics of phase-change optical disk media with a recording layer made of either Ge2Sb2Te5 or Ge19Sb25Te56 alloys were investigated at very high linear velocities ranging from 10 m/s to 60 m/s. We used transmission electron microscope to observe incompletely erased marks, and used computer simulation to treat laser beam heating process in terms of time and temperature. Following results were obtained. (1) The crystallization times, in which the amorphous marks can be erased completely, for Ge19Sb25Te56 and Ge2Sb2Te5 recording films are 55 ns and less than 33 ns respectively. (2) The erasing ratio of Ge19Sb25Te56 disk degrades at high linear velocity (higher than 40 m/s). (3) The erasing ratio degradation is caused by decreasing the number of crystals formed in the marks. (4) When the annealing time τ50 is less than 55 ns, nucleation process becomes bottleneck for crystallization of Ge19Sb25Te56 recording films, and the nucleation time for each grain in the marks is different from one another.
Calculation of the dynamics of surface melting during laser annealing
We present a thermal transport model to describe the melting and resolidification of semiconductors which is observed to occur during annealing with a pulsed laser. The temperature‐dependent properties of both the solid and liquid are included. We compare this calculation with experimental results for the time duration of the melted surface for crystalline Si and Ge. The temperature of the liquid surface as a function of time is calculated and effects associated with the hot liquid and the vapor are also discussed.