STUDY OF SE-TE-SB SYSTEM FOR APPLICATION TO REVERSIBLE OPTICAL-DATA STORAGE

In the present work variation of the two main parameters-viscosity and critical cooling rate, required for the recent upcoming optical data storage devices, have been analysed for different compositions of Se80 -xSbxTe20 (0 less-than-or-equal-to x less-than-or-equal-to 9) system. Temperature dependence of viscosity has been determined using the acti vation energy for glass transition and for crystallization obtained fr om heating rate dependence of glass transition temperature and peak cr ystallization temperature from DSC measurements. Vicsocity has been es timated with the help of Vogel-Tamman-Fulcher equation. It has been fo und that for samples containing Sb less-than-or-equal-to 4 at. %, the viscosity increases with the increase in Sb content. Further increase in Sb concentration causes a decrease in the viscosity. These results are consistent with the structural changes taking place in the Se-Te s ystem with increase in Sb content. Using these values of viscosity and kinetics of crystal nucleation and growth process, the time-temperatu re-transformation curves were obtained. The critical cooling rate R(c) is found to increase for Sb > 4 at. %. For good reversible phase chan ge optical recording, the critical cooling rate of the material should be high enough so as to get an erasure time of less than 1 mus. From the analysis of the data the suitability of the SeTeSb system for opti cal recording has been discussed.