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MBE-grown ZnO-based nanostructures for electronics applications

Kennedy, Oscar W; (2019) MBE-grown ZnO-based nanostructures for electronics applications. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Low-dimensional semiconductors have properties di erent from their bulk counterparts and are thus attractive components for future electronic devices. This thesis presents work on ZnO nanostructures and ZnO/ZnMgO nano-heterostructures grown by molecular beam epitaxy (MBE) for electronics applications. ZnO nanostructures are grown by gold-catalysed MBE. We show that the cut of sapphire used as a substrate determines the orientation of one-dimensional nanostructure growth. On C-plane sapphire we grow ZnO nanowires and on R-plane sapphire we grow ZnO nanobelts. The morphology of nanobelts is shown to depend on temperature with tapering reduced at higher temperatures. Field-e ect transistors based on ZnO nanobelts are fabricated to characterize the electronic properties of single nanobelts. ZnO/ZnMgO heterostructure nanowires and nanobelts are grown and characterized. We show abrupt ZnO/ZnMgO interfaces and demonstrate that the core-shell structures in nanowires increase the luminescence intensity of nanowires. Nanobelt heterostructures are characterized optically at both room temperature and cryogenic temperatures showing evidence of quantum con nement in these structures. Scanning transmission electron microscope cathodoluminescence (CL) is performed on single ZnO nanowires. We perform hyperspectral mapping of CL, in which a single nanowire is spatially mapped with full CL spectra collected at each spatial co-ordinate on the nanowire. We achieve record resolution for hyperspectral mapping and deconvolve full spectra into constituent components. This allows us to distinguish surface and defect peaks as well as CL from inter-band processes in ZnO. We perform proof-of-principle studies combining high quality RF superconducting circuits with epitaxial ZnO layers on single sapphire substrates. Such chips can be used for future experiments coupling mechanical degrees of freedom to superconducting qubits for quantum opto-mechanical experiments.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: MBE-grown ZnO-based nanostructures for electronics applications
Event: UCL
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2019. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms.
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology
URI: http://discovery.ucl.ac.uk/id/eprint/10073240
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