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Structural and Magnetic Characterization of 2D van der Waals Materials Using Scanning Transmission Electron Microscopy
Structural and Magnetic Characterization of 2D van der Waals Materials Using Scanning Transmission Electron Microscopy
상세정보
- 자료유형
- 학위논문 서양
- 최종처리일시
- 20250211152035
- ISBN
- 9798384051718
- DDC
- 530
- 저자명
- Ray, Ariana.
- 서명/저자
- Structural and Magnetic Characterization of 2D van der Waals Materials Using Scanning Transmission Electron Microscopy
- 발행사항
- [Sl] : Cornell University, 2024
- 발행사항
- Ann Arbor : ProQuest Dissertations & Theses, 2024
- 형태사항
- 166 p
- 주기사항
- Source: Dissertations Abstracts International, Volume: 86-03, Section: B.
- 주기사항
- Advisor: Muller, David.
- 학위논문주기
- Thesis (Ph.D.)--Cornell University, 2024.
- 초록/해제
- 요약Two-dimensional (2D) van der Waals (vdW) materials offer easily tunable optical, electronic, and magnetic properties when compared to bulk systems. Layered 2D structures are free from interfacial strain and dangling bonds, and their ability to be interchangeably stacked enables flexible engineering of devices and novel correlated electronic states. Recently-discovered 2D magnetic materials have added an exciting design parameter to vdW heterostructures. As silicon-based transistors approach the limits of Moore's law, 2D magnetic spintronics devices using both charge and spin current may spur a new generation of higher-efficiency electronics.In the 2D extreme, defects, strain, and other local variations can have strong impacts on overall properties. High-resolution and sensitive tools are needed to connect macroscopic behaviors to their origins in the microscopic structure. Scanning transmission electron microscopy (STEM) has been a successful 2D materials characterization method because of its sub-Angstrom resolution, wide variety of secondary signals, and increasing electron transmission for thinner specimens. In this dissertation I use Lorentz TEM and 4D-STEM electron diffraction techniques to address longstanding questions about structural and magnetic order in two 2D vdW magnetic systems.As a first topic, I investigate stacking polytypes in intermediate-thickness 2D CrI3 above and below the bulk structural transition temperature (Chapter 3). The interlayer registration in CrI3 determines its magnetic ordering, so understanding the structural phase space of few-layer CrI3 is essential to intentional magnetic design in 2D CrI3-based devices. I find that 2D CrI3, like bilayer CrI3, remains in a monoclinic symmetry at low temperature, but that there are significant mixtures of monoclinic stacking variants separated by domain walls that may disorder the magnetism.As a second topic, I image magnetic ordering in vanadium-doped WS2, demonstrating the first reported Lorentz TEM imaging of a monolayer magnet (Chapter 4). I find that Lorentz TEM contrast manifests unexpectedly in atomically-thin materials, as their flexural rigidity is low enough that they can be bent by the external magnetic field in the microscope. I also discuss the effects of the electron beam on carrier-mediated magnetic systems like dilute magnetic semiconductors, which may have important implications for future characterization of these materials for spintronics devices.
- 일반주제명
- Condensed matter physics
- 일반주제명
- Physics
- 일반주제명
- Materials science
- 일반주제명
- Electromagnetics
- 키워드
- Domains
- 키워드
- Moire
- 기타저자
- Cornell University Physics
- 기본자료저록
- Dissertations Abstracts International. 86-03B.
- 전자적 위치 및 접속
- 로그인 후 원문을 볼 수 있습니다.
MARC
008250123s2024 us c eng d■001000017162632
■00520250211152035
■006m o d
■007cr#unu||||||||
■020 ▼a9798384051718
■035 ▼a(MiAaPQ)AAI31335318
■040 ▼aMiAaPQ▼cMiAaPQ
■0820 ▼a530
■1001 ▼aRay, Ariana.▼0(orcid)0000-0002-9210-4880
■24510▼aStructural and Magnetic Characterization of 2D van der Waals Materials Using Scanning Transmission Electron Microscopy
■260 ▼a[Sl]▼bCornell University▼c2024
■260 1▼aAnn Arbor▼bProQuest Dissertations & Theses▼c2024
■300 ▼a166 p
■500 ▼aSource: Dissertations Abstracts International, Volume: 86-03, Section: B.
■500 ▼aAdvisor: Muller, David.
■5021 ▼aThesis (Ph.D.)--Cornell University, 2024.
■520 ▼aTwo-dimensional (2D) van der Waals (vdW) materials offer easily tunable optical, electronic, and magnetic properties when compared to bulk systems. Layered 2D structures are free from interfacial strain and dangling bonds, and their ability to be interchangeably stacked enables flexible engineering of devices and novel correlated electronic states. Recently-discovered 2D magnetic materials have added an exciting design parameter to vdW heterostructures. As silicon-based transistors approach the limits of Moore's law, 2D magnetic spintronics devices using both charge and spin current may spur a new generation of higher-efficiency electronics.In the 2D extreme, defects, strain, and other local variations can have strong impacts on overall properties. High-resolution and sensitive tools are needed to connect macroscopic behaviors to their origins in the microscopic structure. Scanning transmission electron microscopy (STEM) has been a successful 2D materials characterization method because of its sub-Angstrom resolution, wide variety of secondary signals, and increasing electron transmission for thinner specimens. In this dissertation I use Lorentz TEM and 4D-STEM electron diffraction techniques to address longstanding questions about structural and magnetic order in two 2D vdW magnetic systems.As a first topic, I investigate stacking polytypes in intermediate-thickness 2D CrI3 above and below the bulk structural transition temperature (Chapter 3). The interlayer registration in CrI3 determines its magnetic ordering, so understanding the structural phase space of few-layer CrI3 is essential to intentional magnetic design in 2D CrI3-based devices. I find that 2D CrI3, like bilayer CrI3, remains in a monoclinic symmetry at low temperature, but that there are significant mixtures of monoclinic stacking variants separated by domain walls that may disorder the magnetism.As a second topic, I image magnetic ordering in vanadium-doped WS2, demonstrating the first reported Lorentz TEM imaging of a monolayer magnet (Chapter 4). I find that Lorentz TEM contrast manifests unexpectedly in atomically-thin materials, as their flexural rigidity is low enough that they can be bent by the external magnetic field in the microscope. I also discuss the effects of the electron beam on carrier-mediated magnetic systems like dilute magnetic semiconductors, which may have important implications for future characterization of these materials for spintronics devices.
■590 ▼aSchool code: 0058.
■650 4▼aCondensed matter physics
■650 4▼aPhysics
■650 4▼aMaterials science
■650 4▼aElectromagnetics
■653 ▼aChromium tri-iodide
■653 ▼aDomains
■653 ▼aMoire
■653 ▼aScanning transmission electron microscopy
■653 ▼aTransition metal dichalcogenides
■690 ▼a0611
■690 ▼a0794
■690 ▼a0605
■690 ▼a0607
■71020▼aCornell University▼bPhysics.
■7730 ▼tDissertations Abstracts International▼g86-03B.
■790 ▼a0058
■791 ▼aPh.D.
■792 ▼a2024
■793 ▼aEnglish
■85640▼uhttp://www.riss.kr/pdu/ddodLink.do?id=T17162632▼nKERIS▼z이 자료의 원문은 한국교육학술정보원에서 제공합니다.
