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Connecting Composition-Driven Faceting with Facet-Driven Composition Modulation in GaAs-AlGaAs Core-Shell Nanowires
Nari Jeon1, Daniel Ruhstorfer2, Markus Döblinger3
1Department of Materials Science and Engineering , Northwestern University , Evanston , Illinois 60208 , United States.
Nano Letters
|July 12, 2018
Summary
Facet-dependent bonding drives alloy segregation in core-shell nanowires, not diffusion. Crystal phase engineering can modulate composition for quantum confined structures.
Area of Science:
- Materials Science
- Nanotechnology
- Semiconductor Physics
Background:
- Ternary III-V alloys with tunable bandgaps are crucial for optoelectronic devices.
- Core-shell nanowires offer geometric flexibility in heterostructure design.
- Alloy segregation in epitaxial shells is a common challenge, even without strain.
Purpose of the Study:
- Investigate the driving forces behind alloy segregation in GaAs-AlGaAs core-shell nanowires.
- Understand the role of facet-dependent bonding versus diffusion in segregation.
- Explore strategies to control alloy decomposition and design quantum confined structures.
Main Methods:
- High-resolution scanning transmission electron microscopy (STEM).
- Laser-assisted atom probe tomography (APT).
- Growth-temperature-dependent studies.
- Analysis of interface faceting and 3D composition profiles.
Main Results:
- Facet-dependent bonding preferences, particularly Al on {112} facets, drive alloy enrichment.
- Segregation is attributed to bonding, not kinetically limited diffusion.
- Al-rich nanorings form perpendicular to the growth direction.
- Zincblende insertions within wurtzite structures show Al enrichment, enabling composition modulation.
Conclusions:
- Alloy decomposition in core-shell nanowires is primarily driven by preferential bonding on specific crystallographic facets.
- Crystal phase engineering offers a method to control composition and mitigate segregation.
- Findings provide insights for designing advanced quantum confined optoelectronic devices.
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