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Unveiling the topological quantum effects in defect-engineered topological insulator films
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TitleInfo
Title
Unveiling the topological quantum effects in defect-engineered topological insulator films
Name
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Salehi
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Maryam
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1988-
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Maryam Salehi
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(authority = RULIB)
author
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Oh
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Seongshik
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Seongshik Oh
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Advisory Committee
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chair
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Fabris
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Laura
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Laura Fabris
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Advisory Committee
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internal member
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(type = family)
O'Carroll
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Deirdre
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Deirdre O'Carroll
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Advisory Committee
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internal member
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Feldman
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Leonard
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Leonard Feldman
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Advisory Committee
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outside member
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Garfunkel
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Eric
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Eric Garfunkel
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Advisory Committee
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outside member
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Rutgers University
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School of Graduate Studies
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theses
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2019
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2019-05
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2019
Language
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English
Abstract
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Topological insulators (TIs) are a class of quantum materials where the bulk is insulating, while the surfaces host in-gap metallic states. The topological surface states (TSSs) are described by the Dirac Hamiltonian whose spin is locked to momentum, and as a result their metallic behavior is protected against crystal imperfections. These features of TSS make TIs a unique test bed for exploration of various new physics and applications. However, almost all the first-generation TIs suffered from a high level of defect densities which pushed the Fermi level away from the bulk energy gap (where the Dirac TSS lies) into the conduction band, thereby obscuring the electronic signature of the TSS.
This dissertation seeks to shed light on the physical origins of defects in pnictogen-chalcogenide TIs, as well as the various defect and interface engineering schemes that have been exploited to effectively suppress these defects. Here, we explain how growing TI films on virtually-grown structurally/chemically-compatible substrates led to films with 10 to 100 times lower defect densities compared to the first-generation films, and with the Fermi level being only few tens of meV above the Dirac point. This is followed by a discussion about the important role of an effective capping layer in stabilizing the properties of low-carrier-density TI films. We further discuss how employing such optimally-designed buffer and capping layers along with proper compensation-doping resolved the previously challenging task of carrier-type tunability in TI films. We then expound on how the ultralow-carrier-density Bi2Se3 and Sb2Te3 films enabled the observation of a series of previously unseen topological quantum effects. Additionally, we present how the ultralow-carrier-density Sb2Te3 films allowed us to reach an extreme quantum limit and explore the previously inaccessible zeroth Landau level. Finally, we conclude by providing a summary of results as well as an outlook towards the future of TI research.
This dissertation seeks to shed light on the physical origins of defects in pnictogen-chalcogenide TIs, as well as the various defect and interface engineering schemes that have been exploited to effectively suppress these defects. Here, we explain how growing TI films on virtually-grown structurally/chemically-compatible substrates led to films with 10 to 100 times lower defect densities compared to the first-generation films, and with the Fermi level being only few tens of meV above the Dirac point. This is followed by a discussion about the important role of an effective capping layer in stabilizing the properties of low-carrier-density TI films. We further discuss how employing such optimally-designed buffer and capping layers along with proper compensation-doping resolved the previously challenging task of carrier-type tunability in TI films. We then expound on how the ultralow-carrier-density Bi2Se3 and Sb2Te3 films enabled the observation of a series of previously unseen topological quantum effects. Additionally, we present how the ultralow-carrier-density Sb2Te3 films allowed us to reach an extreme quantum limit and explore the previously inaccessible zeroth Landau level. Finally, we conclude by providing a summary of results as well as an outlook towards the future of TI research.
Subject
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Topic
Material synthesis and characterization
Subject
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Topic
Materials Science and Engineering
Subject
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Topic
Topological insulators -- Defects
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Rutgers University Electronic Theses and Dissertations
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ETD_9600
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1 online resource (xxi, 196 pages) : illustrations
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Ph.D.
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Includes bibliographical references
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School of Graduate Studies Electronic Theses and Dissertations
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rucore10001600001
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NjNbRU
Identifier
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doi:10.7282/t3-6w75-sk39
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(authority = ExL-Esploro)
ETD doctoral
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Rights
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The author owns the copyright to this work.
RightsHolder
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Name
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Salehi
GivenName
Maryam
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Permission or license
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2019-04-23 17:38:08
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Maryam Salehi
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Affiliation
Rutgers University. School of Graduate Studies
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Author Agreement License
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I hereby grant to the Rutgers University Libraries and to my school the non-exclusive right to archive, reproduce and distribute my thesis or dissertation, in whole or in part, and/or my abstract, in whole or in part, in and from an electronic format, subject to the release date subsequently stipulated in this submittal form and approved by my school. I represent and stipulate that the thesis or dissertation and its abstract are my original work, that they do not infringe or violate any rights of others, and that I make these grants as the sole owner of the rights to my thesis or dissertation and its abstract. I represent that I have obtained written permissions, when necessary, from the owner(s) of each third party copyrighted matter to be included in my thesis or dissertation and will supply copies of such upon request by my school. I acknowledge that RU ETD and my school will not distribute my thesis or dissertation or its abstract if, in their reasonable judgment, they believe all such rights have not been secured. I acknowledge that I retain ownership rights to the copyright of my work. I also retain the right to use all or part of this thesis or dissertation in future works, such as articles or books.
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Embargo
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2019-05-31
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2020-05-30
Detail
Access to this PDF has been restricted at the author's request. It will be publicly available after May 30th, 2020.
Copyright
Status
Copyright protected
Availability
Status
Open
Reason
Permission or license
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2019-04-23T19:33:17
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