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Polytypism in GaAs/GaNAs core-shell nanowires
M Yukimune1, R Fujiwara1, T Mita1
1Graduate School of Science and Engineering, Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan.
Nanotechnology
|September 16, 2020
Summary
The crystal structures of gallium arsenide (GaAs) nanowires were investigated, revealing a decrease in wurtzite (WZ) segments with increased nitrogen in the gallium arsenide nitride (GaNAs) shell. Strain from the GaNAs shell is proposed to induce this polytype change.
Area of Science:
- Materials Science
- Nanotechnology
- Solid-State Physics
Background:
- Gallium arsenide (GaAs) nanowires exhibit zinc-blende (ZB) and wurtzite (WZ) crystal structures.
- Understanding polytypism in core-multishell nanowires is crucial for their electronic and optical properties.
Purpose of the Study:
- To investigate the crystal structures of GaAs and GaAs/GaNAs/GaAs core-multishell nanowires.
- To determine the influence of nitrogen incorporation in GaNAs shells on the ZB/WZ polytypism in GaAs nanowires.
Main Methods:
- X-ray diffraction (XRD) for statistical analysis of crystal structure.
- Electron backscattered diffraction (EBSD) for microscopic and statistical resolution of polytypism.
- Analysis of grain maps and size distribution.
Main Results:
- XRD and EBSD confirm the coexistence of ZB and WZ polytypes in all investigated nanowires.
- Increasing nitrogen concentration in the GaNAs shell reduces the fraction of WZ segments.
- Strain induced by the smaller lattice constant of GaNAs shells is proposed to cause the decrease in WZ polytype.
Conclusions:
- The growth of GaNAs shells significantly impacts the polytypism of GaAs nanowires.
- Strain engineering is a key factor in controlling the crystal structure of core-multishell nanowires.
- Polytype switching occurs along the nanowire length, from WZ to ZB with increasing shell nitrogen content.
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