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Epitaxial growth and characterisation of topological semimetal thin films
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Rehaag, Thomas Joseph (2023) Epitaxial growth and characterisation of topological semimetal thin films. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3984199~S15
Abstract
Thin films of novel topological semimetal materials SrMnSb2 and InBi were grown epitaxially for the first time, and the growth parameters required to achieve high quality crystalline films were explored. Characterisation of SrMnSb2 films revealed overrelaxation of the unit cell to significantly beyond the bulk single crystal lattice constants in every dimension (18(3)% volume increase compared to bulk). This phenomenon was present for samples grown on both InAs(001) and GaSb(001) substrates and was accompanied by a change in symmetry corresponding to a half c cell height due to a suppression of Peierls distortion. The mode 36 coherent phonon response was observed in these films, offering potential for exploiting optoelectronic behaviour.
InBi was successfully homoepitaxially and heteroepitaxially grown via the periodic supply epitaxy (PSE) method, and several structural transitions were identified through reflection high energy electron diffraction (RHEED) analysis. Contrasts were drawn between growth modes and morphology for similar films grown by molecular beam epitaxy (MBE). Cleaved InBi(001) single crystal surfaces were examined, exposing possible coexistence of In and Bi surface terminations via the observation of half c height pits with atomic force microscopy (AFM).
Growth and characterisation work was supported by an MBE system that was commissioned during the PhD period, and a detailed account of the design and calibration process is provided. The procedures for preparing substrates and performing in situ analysis were optimised, where InBi samples act as a demonstration of the full chain of techniques. Additionally, several upgrades to an existing MBE system were implemented and utilised to achieve SrMnSb2 film growth.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QC Physics Q Science > QD Chemistry |
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Library of Congress Subject Headings (LCSH): | Thin films, Semimetals, Epitaxy | ||||
Official Date: | July 2023 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Physics | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Bell, Gavin R. | ||||
Format of File: | |||||
Extent: | xiii, 155 pages : colour illustrations, photographs, charts | ||||
Language: | eng |
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