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Metal-Insulator Transition and IR Detection of Thin Films Fabricated by Pulsed Laser Deposition
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- Author / Creator
- Ryan Thomas McGee
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Current thin film technologies and devices require high quality deposits in order to fully extract the potential of the material. Pulsed laser deposition (PLD) is one physical vapour deposition method used to synthesize these high quality complex films. PLD offers the distinct advantage of being able to stoichiometrically transfer the target material onto the substrate, enabling the deposition of extremely complicated multi-cation materials. This thesis focuses on the synthesis, characterization, and implementation of PLD deposited films into microelectromechanical systems (MEMS) and photonic applications. Specifically, VO2 and MoS2 films will be deposited and subsequently investigated for the above mentioned applications.
The research presented in this thesis targets the synthesis, characterization, device integration, and applications fo thin films deposited by PLD. Characterization by multiple forms of microscopy, X-ray diffraction, spectroscopy, electronic response, and photothermal response provide a multitude of new information integral to successful applications. VO2 thin film deposition is optimized by implementation of the Taguchi method, where the influence of each variable is elucidated by analysis of variance. The electronic properties of VO2 are shown to rely heavily on the interfacial structure between the film and substrate, with increased performance present in epitaxial films. Integration into MEMS devices required the development of a full microfabrication process, accounting for the stability of not only VO2, but all other materials during the entire process. Once integrated on MEMS devices, the phase transition of VO2 is manifested as a huge shift in the resonance frequency.
Finally, the mid-IR photothermal response of PLD deposited MoS2 is investigated. Physical defects imparted by the impactive nature of PLD create trap states in the band structure, leading to improved sensitivity to mid-IR. Additionally, interfacial structure was important in the sensitivity, as a twin interface between MoS2 and silicon improved the temperature coefficient of resistance, and ultimately the responsivity.
The conclusion presents a variety of potential applications for both VO2 and MoS2 thin films that have been, or are currently under investigation. The future applications of these materials seems limitless due to the unique properties of both. This thesis closes with an insight into ongoing research applicable to the work already completed.
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- Graduation date
- Fall 2018
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.