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Science 13 November 2009:
Vol. 326. no. 5955, pp. 980 - 984
DOI: 10.1126/science.1177483
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Reports

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

Bong-Sub Lee,1,2 Geoffrey W. Burr,3 Robert M. Shelby,3 Simone Raoux,3,* Charles T. Rettner,3 Stephanie N. Bogle,1,2 Kristof Darmawikarta,1,2 Stephen G. Bishop,2,4 John R. Abelson1,2,{dagger}

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.

1 Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign (UIUC), Urbana, IL 61801, USA.
2 Coordinated Science Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
3 IBM/Macronix Phase Change Random Access Memory Joint Project, IBM Almaden Research Center, San Jose, CA 95120, USA.
4 Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.

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

{dagger} To whom correspondence should be addressed. E-mail: abelson{at}illinois.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Viewing the Seeds of Crystallization.
J. M. Gibson (2009)
Science 326, 942-943
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