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Fast Crystallization of the Phase Change Compound GeTe by Large-Scale Molecular Dynamics Simulations
Gabriele C Sosso1,2, Giacomo Miceli3, Sebastiano Caravati1
1†Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via R. Cozzi 53, I-20125 Milano, Italy.
The Journal of Physical Chemistry Letters
|August 22, 2015
Summary
Fast crystallization in phase change materials like GeTe is driven by rapid atomic mobility in supercooled liquids, not nucleation limits. This explains their use in rewritable optical disks and electronic memories.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Computational Chemistry
Background:
- Phase change materials are crucial for rewritable optical disks and electronic nonvolatile memories.
- Their function relies on rapid, reversible amorphous-to-crystalline phase transitions (nanosecond timescale).
Purpose of the Study:
- Investigate the microscopic origins of fast crystallization in phase change materials.
- Understand the crystallization process in GeTe for memory applications.
Main Methods:
- Large-scale molecular dynamics simulations.
- Utilized a Neural Network-fitted interatomic potential based on ab initio energies.
Main Results:
- In the 500–700 K range relevant to electronic memories, crystal nucleation is not the rate-limiting step.
- Fast growth of supercritical nuclei is observed due to high atomic mobility.
- High liquid fragility and Stokes-Einstein relation breakdown contribute to rapid atomic mobility.
Conclusions:
- The fast crystallization of GeTe is primarily governed by rapid nucleus growth, not nucleation.
- Understanding atomic mobility in supercooled liquids is key to optimizing phase change material performance in memory devices.
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