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Nature of phase transitions in crystalline and amorphous GeTe-Sb2Te3 phase change materials.

Authors :
Kalkan B
Sen S
Clark SM
Source :
The Journal of chemical physics [J Chem Phys] 2011 Sep 28; Vol. 135 (12), pp. 124510.
Publication Year :
2011

Abstract

The thermodynamic nature of phase stabilities and transformations are investigated in crystalline and amorphous Ge(1)Sb(2)Te(4) (GST124) phase change materials as a function of pressure and temperature using high-resolution synchrotron x-ray diffraction in a diamond anvil cell. The phase transformation sequences upon compression, for cubic and hexagonal GST124 phases are found to be: cubic → amorphous → orthorhombic → bcc and hexagonal → orthorhombic → bcc. The Clapeyron slopes for melting of the hexagonal and bcc phases are negative and positive, respectively, resulting in a pressure dependent minimum in the liquidus. When taken together, the phase equilibria relations are consistent with the presence of polyamorphism in this system with the as-deposited amorphous GST phase being the low entropy low-density amorphous phase and the laser melt-quenched and high-pressure amorphized GST being the high entropy high-density amorphous phase. The metastable phase boundary between these two polyamorphic phases is expected to have a negative Clapeyron slope.<br /> (© 2011 American Institute of Physics)

Details

Language :
English
ISSN :
1089-7690
Volume :
135
Issue :
12
Database :
MEDLINE
Journal :
The Journal of chemical physics
Publication Type :
Academic Journal
Accession number :
21974538
Full Text :
https://doi.org/10.1063/1.3643327