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Photoexcitation Induced Ultrafast Nonthermal Amorphization in Sb2Te3
Subodh C Tiwari1, Rajiv K Kalia1, Aiichiro Nakano1
1Collaboratory for Advanced Computing and Simulation, Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90007, United States.
The Journal of Physical Chemistry Letters
|November 19, 2020
Summary
Phase-change materials like Sb2Te3 can be rapidly amorphized using photoexcitation. This nonthermal pathway reduces energy and time, enhancing optoelectronic devices for neuromorphic computing.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Computational Chemistry
Background:
- Phase-change materials (PCMs) are crucial for low-power, high-throughput storage in neuromorphic computing.
- Sb2Te3, a Ge-Sb-Te alloy, offers fast, energy-efficient switching between amorphous and crystalline states.
- Its crystallization is growth-dominated, unlike Ge2Sb2Te5's nucleation-dominated process.
Purpose of the Study:
- To investigate a nonthermal photoexcitation pathway for reducing amorphization energy and time in Sb2Te3.
- To explore the effects of varying photoexcited valence electron-hole carrier concentrations on Sb2Te3 amorphization.
Main Methods:
- Nonadiabatic quantum molecular dynamics simulations were used.
- Simulations analyzed the time evolution of Sb2Te3 under photoexcitation (2.6% to 12.5% carriers).
Main Results:
- Amorphization degree increased with photoexcitation, saturating at 10.3% excitation.
- Rapid amorphization resulted from Te-p to Sb-p orbital charge transfer and Sb-Te bonding changes.
- Higher excitation (≥7.5%) induced atomic diffusion and irreversible loss of long-range order.
Conclusions:
- Photoexcitation offers an ultrafast, energy-efficient amorphization pathway for Sb2Te3.
- This nonthermal method can enhance the performance of phase-change material-based optoelectronic devices.
