Nature of phase transitions in crystalline and amorphous GeTe-Sb 2Te3 phase change materials

B. Kalkan, S. Sen*, S. M. Clark

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)


The thermodynamic nature of phase stabilities and transformations are investigated in crystalline and amorphous Ge1Sb2Te 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.

Original languageEnglish
Article number124510
Pages (from-to)1-9
Number of pages9
JournalJournal of Chemical Physics
Issue number12
Publication statusPublished - 28 Sept 2011
Externally publishedYes


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