Characterization and Application of Transition-Metal Dichalcogenides with Rapid Second Harmonic Generation Imaging
- 주제(키워드) second harmonic generation , transition-metal dichalcogenides , laser thinning , microbial strain , label-free sensing
- 주제(DDC) 621.042
- 발행기관 아주대학교 일반대학원
- 지도교수 Yeong Hwan Ahn
- 발행년도 2024
- 학위수여년월 2024. 2
- 학위명 박사
- 학과 및 전공 일반대학원 에너지시스템학과
- 실제URI http://www.dcollection.net/handler/ajou/000000033500
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
Second harmonic generation (SHG) imaging has been formulated and extended to investigate the nonlinear properties and crystallography in transition-metal dichalcogenides (TMDs). This thesis delves deeply into the exploration and understanding of transition-metal dichalcogenides (TMDs) layers using rapid second harmonic generation (SHG) imaging. Our investigation process using rapid SHG imaging led us to the characterization of these TMD layers, focusing particularly on aspects of crystallinity such as orientation and homogeneity. A noteworthy observation was made regarding the twisted bilayer MoS2. In this thesis, we unraveled a complex relationship between the intensity of SHG and the twist angle. A further in-depth examination of this relationship was carried out by examining the effects of strong interlayer coupling, which were substantiated by measurements of photoluminescence (PL). In our research, we observed the in situ processing of bilayer MoS2 using femtosecond laser ablation techniques. By mapping out critical threshold behaviors, we pinpointed optimal laser processing conditions essential for precise layer-by- layer manipulation of TMDs. This revelation of laser-induced thresholds became instrumental in the precise control of TMDs, opening doors to potential advancements in optoelectronic device fabrication. One of the most groundbreaking findings was the transformative role of bacteria on SHG signals in monolayer MoS2 flakes. There was an anisotropic enhancement of SHG in the presence of single-celled bacteria on monolayer TMD, with strain effects caused by bacteria. This discovery not only magnifies SHG imaging sensitivity to biomaterial strains on the surfaces but also introduces a promising frontier in harnessing this phenomenon for innovative optical and optoelectronic devices. Finally, as a result of our research, we have been able to provide an innovative approach to the detection and identification of different types of microbial. By capturing transient SHG signals during the cell rupture process, we were successful in discerning different bacterial species. This proficiency introduces a revolutionary path to label-free detection in single cells, thereby augmenting the toolkit for enhanced diagnostic procedures. In summary, this research propounds significant advancements in our comprehension of TMDs, enriching the potential applications of SHG imaging in both the scientific and technological landscapes.
more목차
Chapter 1 Introduction 1
1.1 Overview of SHG Imaging in 2D Materials . 1
1.2 Outline of the Thesis 2
Chapter 2 Background 4
2.1 Principles of Nonlinear Optical Response . 4
2.2 Second Harmonic Generation (SHG) 5
2.3 Transitional-metal Dichalcogenides (TMDs) 8
2.4 SHG Processes in TMDs 9
2.5 SHG Modulation in TMDs 11
2.5.1 Twist Angle Dependent SHG in Bilayer TMDs . 12
2.5.2 Strain induced SHG modulation. 16
2.6 Laser Ablation. 19
Chapter 3 In-situ SHG Imaging in Twisted Bilayer MoS2 25
3.1 Introduction . 25
3.2 Methods . 27
3.3 High-Speed SHG Imaging Setup 28
3.4 Analysis of SHG Intensity in Twisted Bilayer MoS2 . 31
3.5 Summary 35
Chapter 4 Femtosecond Laser Induced Layer-by-Layer Thinning in Twisted Bilayer MoS2 36
4.1 Introduction . 36
4.2 Analysis of Laser Ablation in Monolayer MoS2 37
4.3 Layer-by-Layer Control in Twisted Bilayer MoS2 40
4.4 Summary 43
Chapter 5 Microbial Control Over SHG in Monolayer MoS2 . 44
5.1 Introduction . 44
5.2 Methods . 45
5.3 SHG Imaging for Biomaterial Strain Monitoring 48
5.4 Summary 62
Chapter 6 Label-free Single Bacteria Identification with Rapid SHG imaging 63
6.1 Introduction . 63
6.2 SHG Imaging for MoS2 Bacteria Monitoring 66
6.3 Transient SHG Signals and Rupture Times Analysis. 69
6.4 Distinction of Different Bacterial Species in Single Cell Level 71
6.5 Summary 77
Chapter 7 Conclusions and Outlook 78
Appendix 80
Appendix A Scanning Photocurrent Microscopy on TMD heterostructure devices 80
Appendix B Rapid THZ Time-of-Flight Imaging for Conductivity Assessment of Graphene 93
Bibliography 108
국문 요약 132
List of Publication 134
