Abstract
ABSTRACTThe bit-erase process in phase-change optical storage is based on the amorphous to crystalline transformation. While there has been significant progress developing compositions and multilayered media for phase-change applications, quantitative studies of the crystallization kinetics and microstructural development are generally lacking. This paper describes work quantifying crystallization in GeTe thin films. Microstructural changes during isothermal annealing are measured usingin-situhot-stage optical microscopy. This technique measures the fraction crystallized, the number of crystallites, and crystallite radii as a function of time. These data are sufficient to deconvolute the individual contributions of nucleation and growth. We find an Avrami exponent of ∼4, consistent with time-resolved reflection/transmission studies. This exponent is due to 2-D growth at a constant rate plus transient nucleation. The data are used in a kinetic model to simulate non-isothermal crystallization during focused-laser heating characteristic of the bit-erase process.
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