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Phase change materials: From structures to kinetics

Published online by Cambridge University Press:  31 January 2011

Wojciech Wełnic*
Affiliation:
I. Physikalisches Institut (IA), Rheinisch-Westfâlisch Technische Hochschule (RWTH) Aachen University of Technology, 52056 Aachen, Germany
Johannes A. Kalb
Affiliation:
I. Physikalisches Institut (IA), Rheinisch-Westfâlisch Technische Hochschule (RWTH) Aachen University of Technology, 52056 Aachen, Germany
Daniel Wamwangi
Affiliation:
I. Physikalisches Institut (IA), Rheinisch-Westfâlisch Technische Hochschule (RWTH) Aachen University of Technology, 52056 Aachen, Germany
Christoph Steimer
Affiliation:
I. Physikalisches Institut (IA), Rheinisch-Westfâlisch Technische Hochschule (RWTH) Aachen University of Technology, 52056 Aachen, Germany
Matthias Wuttig
Affiliation:
I. Physikalisches Institut (IA), Rheinisch-Westfâlisch Technische Hochschule (RWTH) Aachen University of Technology, 52056 Aachen, Germany
*
a)Address all correspondence to this author. Present address: Laboratoire des Solides Irradiés, CNRS-CEA, École Polytechnique, Palaiseau, France, European Theoretical Spectroscopy Facility (ETSF). e-mail: welnic@physik.rwth-aachen.de
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Abstract

Phase change materials possess a unique combination of properties, which includes a pronounced property contrast between the amorphous and crystalline state, i.e., high electrical and optical contrast. In particular, the latter observation is indicative of a considerable structural difference between the amorphous and crystalline state, which furthermore is characterized by a very high vacancy concentration unknown from common semiconductors. Through the use of ab initio calculations, this work shows how the electric and optical contrast is correlated with structural differences between the crystalline and the amorphous state and how the vacancy concentration controls the optical properties. Furthermore, crystal nucleation rates and crystal growth velocities of various phase change materials have been determined by atomic force microscopy and differential thermal analysis. In particular, the observation of different recrystallization mechanisms upon laser heating of amorphous marks is explained by the relative difference of just three basic parameters among these alloys, namely, the melt-crystalline interfacial energy, the entropy of fusion, and the glass transition temperature.

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Type
Outstanding Meeting Paper
Copyright
Copyright © Materials Research Society 2007

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