LASER-INDUCED CRYSTALLIZATION IN GE-SB-TE OPTICAL-RECORDING MATERIALS

Laser-induced crystallization behaviour in Ge-Sb-Te optical recording thin film materials, that are sandwiched between dielectric layers, wa s studied by a multipulse laser technique. The reflection changes at 7 80 nm laser wavelength caused by local heating by a pulsed high-power laser beam are monitored. Both the nucleation time and the complete cr ystallization time are found to decrease significantly with increasing phase change layer thickness up to about 25 nm, above which both tend to become constant. Furthermore, the maximum crystallization speed de pends on the type of dielectric material. The strong dependence of cry stallization speed on layer thickness is explained in terms of competi ng interface and bulk processes. This finding is of practical use beca use it allows the design of phase change optical recording media which can be used at high linear recording speeds. (C) 1997 Elsevier Scienc e S.A.