Ferroelectric domain structures of twisted transition metal dichalcogenide bilayers investigated by scanning probe microscopy
- 주제(키워드) ferroelectrics , moiré superlattices , atomic reconstruction , domain , domain wall network , piezoresponse force microscopy , kelvin probe force microscopy
- 발행기관 서강대학교 일반대학원
- 지도교수 양상모
- 발행년도 2026
- 학위수여년월 2026. 2
- 학위명 박사
- 학과 및 전공 일반대학원 물리학과
- 실제URI http://www.dcollection.net/handler/sogang/000000082657
- UCI I804:11029-000000082657
- 본문언어 영어
- 저작권 논문은 저작권에 의해 보호받습니다.
목차
Abstract (English) ⅰ
Contents iv
List of Figures ⅷ
Chapter 1. Introduction 1
1.1 Ferroelectric domains 1
1.2 Ferroelectricity in perovskite oxides 3
1.3 Two-dimensional van der Waals heterostructures 5
1.3.1 Van der Waals layered homo- and heterostructures 5
1.3.2 Interlayer interactions in Frenkel-Kontorova model 7
1.4 Stacking angle engineered 2D moiré materials 9
1.5 Outline of this thesis 12
Chapter 2. Visualization of moiré patterns in marginally twisted TMD 16
2.1 Non-centrosymmetric TMD structure 16
2.1.1 TMD monolayers 16
2.1.2 Moiré superlattices in twisted bilayer TMD 17
2.1.3 Sample preparation for twisted bilayer TMD 19
2.2 Visualization of ferroelectric domains 20
2.2.1 Vertical piezoelectric force microscopy 20
2.2.2 PFM imaging of multidomain structures 25
2.2.3 Setup of preparation on PFM 28
2.3 Moiré ferroelectric domain structures in twisted bilayer WSe2 31
2.3.1 DFRT-PFM imaging of triangular domains 31
2.3.2 Edge polarization 34
2.4 Summary 36
Chapter 3. Mechanical properties in reconstructed TMD bilayers 41
3.1 Permanent two-dimensional flexure in vdW layers 41
3.2 Movement of a two-dimensional flexure 42
3.2.1 Ripplocation ; relocating the dislocations 42
3.2.2 Moiré pattern movement by sliding-disturbance 47
3.2.3 Effects of topographical hill sites 48
3.3 Mechanical perturbation reveals topological protection 49
3.3.1 KPFM imaging 49
3.3.2 Dynamic triggering process 50
3.3.3 Robust MM region vs. Displaceable MM region 51
3.3.4 Fragmented fourfold pattern 55
3.4 Toplological order in domain configurations 57
3.4.1 Electron diffraction and dark field image analysis 57
3.4.2 Concentration of domain wall network 60
3.5 Summary 62
Chapter 4. Thermal effects to the domain wall dynamics 67
4.1 Landau theory in moiré ferroelectric heterostructure 67
4.2 Investigation about thermodynamic effects to the domain walls 72
4.2.1 Backgrounds 72
4.2.2 Heater stage setup 73
4.2.3 Temperature calibration 76
4.3 Structural preservation of R-stacking in high temperature 77
4.4 Domain wall displacements in ambient vs. high temperature 81
4.5 Summary 86
Chpater 5. Perspectives 90
5.1 Insights into novel reconstruction 90
5.2 Summary 93
Abstract in Korean 96
