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Size Dependence of Structural Metastability in Semiconductor Nanocrystals
1Department of Chemistry, University of California, Berkeley, and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
Science (New York, N.Y.)
|April 18, 1997
Summary
Nanocrystal phase transitions follow simple unimolecular kinetics, differing from bulk solids. Barrier heights increase with nanocrystal size, offering insights into new metastable phase discovery.
Area of Science:
- Materials Science
- Nanotechnology
- Solid-State Chemistry
Background:
- Bulk solids exhibit complex phase transition kinetics.
- Nanocrystals present unique behaviors due to their size and surface area.
- Understanding phase transitions in nanomaterials is crucial for advanced applications.
Purpose of the Study:
- Investigate the kinetics of solid-solid phase transitions in cadmium selenide (CdSe) nanocrystals.
- Determine the influence of crystallite size on phase transition mechanisms.
- Explore the relationship between surface properties and transition barriers.
Main Methods:
- Studied the prototypical CdSe nanocrystal system.
- Analyzed phase transitions as a function of crystallite size.
- Characterized transformations using unimolecular kinetics models.
Main Results:
- Nanocrystals undergo phase transitions via single nucleation events.
- Observed simple unimolecular kinetics for these transformations.
- Found that barrier heights increase with nanocrystal size.
- Noted dependence of barrier heights on nanocrystal surface nature.
Conclusions:
- Nanocrystal phase transitions are distinct from extended solids.
- Results suggest generalizable rules for discovering new metastable phases.
- Findings are analogous to magnetic phase transitions in nanocrystals.