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Exploring the limits of fast phase change materials

Published online by Cambridge University Press:  21 March 2011

Han-Willem Wöltgens ,
Ralf Detemple ,
Inés Friedrich ,
Walter K. Njoroge ,
Ingo Thomas ,
Volker Weidenhof ,
Stefan Ziegler  and
Matthias Wuttig
Han-Willem Wöltgens
Affiliation:
I. Physikalisches Institut der RWTH-Aachen, D-52056 Aachen, Germany
Ralf Detemple
Affiliation:
I. Physikalisches Institut der RWTH-Aachen, D-52056 Aachen, Germany
Inés Friedrich
Affiliation:
I. Physikalisches Institut der RWTH-Aachen, D-52056 Aachen, Germany
Walter K. Njoroge
Affiliation:
I. Physikalisches Institut der RWTH-Aachen, D-52056 Aachen, Germany
Ingo Thomas
Affiliation:
I. Physikalisches Institut der RWTH-Aachen, D-52056 Aachen, Germany
Volker Weidenhof
Affiliation:
I. Physikalisches Institut der RWTH-Aachen, D-52056 Aachen, Germany
Stefan Ziegler
Affiliation:
I. Physikalisches Institut der RWTH-Aachen, D-52056 Aachen, Germany
Matthias Wuttig
Affiliation:
I. Physikalisches Institut der RWTH-Aachen, D-52056 Aachen, Germany
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Abstract

In the last decade a number of chalcogenide alloys, including ternary alloys of GeSbTe and quaternary alloys of InAgSbTe, have been identified which enable fast phase change recording. In the quest for materials with improved phase change kinetics we present two different approaches. By comparing alloys with well-defined stoichiometries the mechanisms which govern the transformation kinetics are determined. Optical and electrical measurements determine the activation energy for crystallization to 2.24 ± 0.11 eV for Ge2Sb2Te5 and to 3.71 ± 0.07 eV for Ge4Sb1Te5, respectively. It is shown that for GeSbTe-alloys with different composition the activation energy increases linearly with increasing Ge content. Power-time- reflectivity change diagrams recorded with a static tester reveal that Ge2Sb2Te5, in agreement with previous data, recrystallizes by the growth of sub critical nuclei, while Ge4Sb1Te5 grows from the crystalline rim surrounding the bit.

To speed up the search for faster materials we employ concepts of combinatorial material synthesis by producing films with a stoichiometry gradient. Then laterally resolved secondary neutral mass spectroscopy (SNMS) combined with the static tester are used to identify the composition with superior properties for phase change applications.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 674: Symposia T/U/V – Applications of Ferromagnetic and Optical Materials, Storage and Magnetoelectronics , 2001 , V1.3
Copyright
Copyright © Materials Research Society 2001

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References

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