Dynamics of a Droplet that Assists III-V Nanowire Growth
Summary, in English
This thesis explores the fundamental limits for one-directional droplet-assisted crystal growth. This is studied first by intentionally displacing the droplet from the facet at which it originally assisted the crystal growth. The process and cause for displacement is studied for Au-assisted GaAs and InAs nanowires by combining experimental observations and theoretical modeling of the droplet wetting. In addition, it is shown that the final position of the droplet can be controlled by tailoring the surfaces of the nanowire, which in turn is used for design of branched structures. Furthermore, this thesis focuses on the droplet dynamics and the formation of a truncation at the droplet-nanowire interface, as the geometry of the droplet wetting of the top facet approaches the fundamental limit.
The studies of this thesis are conducted using metal-organic chemical vapor deposition (MOCVD), both in- and outside an environmental transmission electron microscope (ETEM). Ex-situ analysis of droplet displacement allows us to investigate the statistics of the process, to understand trends of the droplet wetting. On the other hand, performing MOCVD inside an ETEM enables real-time studies of the dynamic processes during growth, such as observations of the droplet wetting angle or the facet truncation. Using a combination of theoretical modeling, high-temperature X-ray energy dispersive spectroscopy and direct imaging during growth, we measure and estimate the previously inaccessible gallium and arsenic concentration in the droplet, as well as the surface energies of the Au-Ga droplet and the GaAs nanowire sidewalls. These findings could in turn be used to further improve our understanding of the atomic arrangement at
the crystal surfaces and interfaces during growth. Such an understanding could lead to improved control and design of crystal nanostructures.
- Materials Chemistry
- Other Physics Topics
- Nano Technology
- Crystal growth
- III-V semiconductor nanowires
- Environmental transmission electron mircoscopy
- X-ray energy-dispersive spectroscopy
- Fysicumarkivet A:2020:Tornberg
- Kimberly Dick Thelander
- Sebastian Lehmann
- Reine Wallenberg
- ISBN: 978-91-7895-486-5
- ISBN: 978-91-7895-487-2
4 May 2020
Lecture hall Rydbergssalen, Department of Physics, Sölvegatan 14, Faculty of Engineering LTH, Lund University, Lund.
- Michael Filler (Prof.)