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The role of vacancies in the pressure amorphisation phenomenon observed in Ge-Sb-Te phase change alloys

Published online by Cambridge University Press:  01 February 2011

Milos Krbal ,
Alex Kolobov ,
Paul Fons ,
Junji Tominaga ,
Julien Haines ,
Annie Pradel ,
Michel Ribes ,
Claire Levelut ,
Rozenn Le Parc  and
Michael Hanfland
Milos Krbal
Affiliation:
milos.krbal@aist.go.jp, National Institute of Advanced Industrial Science and Technology, Nanodevice Innovation Research Centre, Tsukuba, Japan
Alex Kolobov
Affiliation:
a.kolobov@aist.go.jp, United States
Paul Fons
Affiliation:
paul-fons@aist.go.jp, National Institute of Advanced Industrial Science and Technology, Nanodevice Innovation Research Centre, Tsukuba, Japan
Junji Tominaga
Affiliation:
j-tominaga@aist.go.jp, National Institute of Advanced Industrial Science and Technology, Nanodevice Innovation Research Centre, Tsukuba, Japan
Julien Haines
Affiliation:
Julien.Haines@univ-montp2.fr, Institute Charles Gerhardt, UMR 5253 CNRS-UM2-ENSCM-UM1, PMDP/PMOF, Université Montpellier II, Montpellier, France
Annie Pradel
Affiliation:
apradel@lpmc.univ-montp2.fr, Institute Charles Gerhardt, UMR 5253 CNRS-UM2-ENSCM-UM1, PMDP/PMOF, Université Montpellier II, Montpellier, France
Michel Ribes
Affiliation:
mribes@lpmc.univ-montp2.fr, Institute Charles Gerhardt, UMR 5253 CNRS-UM2-ENSCM-UM1, PMDP/PMOF, Université Montpellier II, Montpellier, France
Claire Levelut
Affiliation:
claire@lcvn.univ-montp2.fr, Université Montpellier II, Laboratoire des Colloides, Verres et Nanomatériaux, Montpellier, France
Rozenn Le Parc
Affiliation:
leparc@lcvn.univ-montp2.fr, Université Montpellier II, Laboratoire des Colloides, Verres et Nanomatériaux, Montpellier, France
Michael Hanfland
Affiliation:
hanfland@esrf.fr, European Synchrotron Radiation Facility, Grenoble, France
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Abstract

We demonstrate, both experimentally and by computer simulation, that while the metastable face-centered cubic (fcc) phase of Ge-Sb-Te becomes amorphous under hydrostatic compression at about 15 GPa, the stable trigonal phase remains crystalline. We present evidences that the pressure-induced amorphisation phenomenon strongly depends on the concentration of vacancies included in the Ge/Sb sublattice, but is thermally insensitive. Upon higher compression, a body-centered cubic phase is obtained in both cases at around 30 GPa. Upon decompression, the amorphous phase is retained when starting with the fcc phase while the initial structure is recovered when starting with the trigonal phase. We argue that the presence of vacancies and the associated subsequent large atomic displacements lead to nanoscale phase separation and the loss of the initial structure memory in the fcc staring phase of Ge-Sb-Te. We futher compare the amorphous phase obtained via the pressure route with the melt quenched amorphous phase.

Keywords

phase transformationsimulationx-ray diffraction (XRD)
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1251: Symposium H – Phase-Change Materials for Memory and Reconfigurable Electronics Applications , 2010 , 1251-H04-10
Copyright
Copyright © Materials Research Society 2010

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