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Nature of phase transitions in crystalline and amorphous GeTe-Sb2Te3 phase change materials.
- Source :
- Journal of Chemical Physics; 9/28/2011, Vol. 135 Issue 12, p124510, 9p
- Publication Year :
- 2011
-
Abstract
- The thermodynamic nature of phase stabilities and transformations are investigated in crystalline and amorphous Ge1Sb2Te4 (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. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00219606
- Volume :
- 135
- Issue :
- 12
- Database :
- Complementary Index
- Journal :
- Journal of Chemical Physics
- Publication Type :
- Academic Journal
- Accession number :
- 66184674
- Full Text :
- https://doi.org/10.1063/1.3643327