Droplet-mediated formation of embedded GaAs nanowires in MBE GaAs1−xBixfilms
| Autor: | Jincheng Li, April S. Brown, Adam W. Wood, Susan E. Babcock, Kristen Collar |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
010302 applied physics
Materials science business.industry Mechanical Engineering Nanowire Bioengineering 02 engineering and technology General Chemistry Substrate (electronics) 021001 nanoscience & nanotechnology Epitaxy 01 natural sciences Dark field microscopy Optics Mechanics of Materials Transmission electron microscopy 0103 physical sciences Scanning transmission electron microscopy Microscopy Optoelectronics General Materials Science Electrical and Electronic Engineering 0210 nano-technology business Molecular beam epitaxy |
| Zdroj: | Nanotechnology. 27:115704 |
| ISSN: | 1361-6528 0957-4484 |
| DOI: | 10.1088/0957-4484/27/11/115704 |
| Popis: | We have examined the morphology and composition of embedded nanowires that can be formed during molecular beam epitaxy of GaAs(1-x)Bi(x) using high angle annular dark field ('Z-contrast') imaging in an aberration-corrected scanning transmission electron microscope. Samples were grown in Ga-rich growth conditions on a stationary GaAs substrate. Ga-rich droplets are observed on the surface with lateral trails extending from the droplet in the [110] direction. Cross-sectional scanning transmission electron microscopy of the film reveals epitaxial nanowire structures of composition ∼GaAs embedded in the GaAs(1-x)Bi(x) epitaxial layers. These nanowires extend from a surface droplet to the substrate at a shallow angle of inclination (∼4°). They typically are 4 μm long and have a lens-shaped cross section with major and minor axes dimensions of 800 and 120 nm. The top surface of the nanowires exhibits a linear trace in longitudinal cross-section, across which the composition change from ∼GaAs to GaAs(1-x)Bi(x) appears abrupt. The bottom surfaces of the nanowires appear wavy and the composition change appears to be graded over ∼25 nm. The droplets have phase separated into Ga- and Bi-rich components. A qualitative model is proposed in which Bi is gettered into Ga droplets, leaving Bi depleted nanowires in the wakes of the droplets as they migrate in one direction across the surface during GaAs(1-x)Bi(x) film growth. |
| Databáze: | OpenAIRE |
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