LASER-INDUCED CRYSTALLIZATION PHENOMENA IN GETE-BASED ALLOYS .1. CHARACTERIZATION OF NUCLEATION AND GROWTH

The laser-induced crystallization behavior of GeTe-based amorphous all oy thin films has been quantitatively studied by local reflection meas urements with a focused 780 nm laser. The use of multiple laser pulse sequences enables the nucleation rate and crystal-growth speed to be s eparately deduced, allowing the compositional variation of both these processes to be followed. This not only gives detailed information on the crystallization mechanism, but also allows the fine tuning of phas e change ahoy compositions for use in erasable optical recording. The differences between the as-deposited and melt-quenched amorphous phase s are also discussed. In particular, it is shown that the crystallizat ion speed of the as-deposited layer can differ by over an order of mag nitude from that of the melt-quenched amorphous layer. The as-deposite d state can, however, be transformed into a modified amorphous state e quivalent to that obtained by melt quenching a previously crystalline layer. This allows the determination of the optical constants and crys tallization speeds of the amorphous state written during optical recor ding. (C) 1995 American Institute of Physics.