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Observation of the Role of Subcritical Nuclei in Crystallization of a Glassy Solid

Science  13 Nov 2009:
Vol. 326, Issue 5955, pp. 980-984
DOI: 10.1126/science.1177483

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Abstract

Phase transformation generally begins with nucleation, in which a small aggregate of atoms organizes into a different structural symmetry. The thermodynamic driving forces and kinetic rates have been predicted by classical nucleation theory, but observation of nanometer-scale nuclei has not been possible, except on exposed surfaces. We used a statistical technique called fluctuation transmission electron microscopy to detect nuclei embedded in a glassy solid, and we used a laser pump-probe technique to determine the role of these nuclei in crystallization. This study provides a convincing proof of the time- and temperature-dependent development of nuclei, information that will play a critical role in the development of advanced materials for phase-change memories.

  • * Present address: IBM T. J. Watson Research Center, Yorktown Heights, NY 10598, USA.

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