Synthesis and Characterizations of W-based two-dimensional nanomaterials and alloys
- 주제(키워드) Synthesis , W-based , 2D nanomaterials
- 주제(DDC) 621.042
- 발행기관 아주대학교 일반대학원
- 지도교수 Ji-Yong Park
- 발행년도 2026
- 학위수여년월 2026. 2
- 학위명 박사
- 학과 및 전공 일반대학원 에너지시스템학과
- 실제URI http://www.dcollection.net/handler/ajou/000000035442
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
In this thesis, we discussed the synthesis and characterization of tungsten (W)-based two-dimensional (2D) nanomaterials and their alloys, aiming to expand their applicability in next-generation electronics, catalysis, and energy storage. Using controlled chemical vapor deposition (CVD) methods, various W-based 2D structures–including WS2, WSe2 and their alloyed forms–were synthesized with tunable compositions and morphologies. Initial characterization of the as-grown W-based materials, such as their shapes, sizes, and coverages, is performed using an optical microscope (OM). Further morphological and height analysis of individual W-based flakes is conducted using an AFM (XE-100 from Park Systems). Raman and PL measurements are carried out using a 532 nm laser excitation source (XperRAM from Nanobase). The electrical transport properties of W-based devices are measured using a parameter analyzer (4200A-SCS from Keithley) in ambient condition. Maskless lithography (LITHO MASKLESS from Planck Inc.) is used to define electrode patterns for W-based field effect transistor (FET) devices on the as-grown substrate. Electrodes are deposited via e-beam evaporation, followed by a lift-off process to complete the device fabrication. The findings presented in this thesis contribute to the fundamental understanding of W-based 2D materials and alloys, paving the way for their integration into next- generation nanodevices and energy technologies.
more목차
Chapter 1. Introduction 1
1.1. Transition Metal Dichalcogenides (TMDs) 1
1.2. W-based TMDs 2
1.3. Research Motivation and Objectives 2
1.4. Thesis Outline 3
1.5. References 5
Chapter 2. Theoretical Background 6
2.1. Introduction to Two-Dimensional (2D) Materials 6
2.2. Transition Metal Dichalcogenides (TMDs) 6
2.3. Tungsten-Based 2D Nanomaterials 7
2.3.1. Crystal Structure 7
2.3.2. Symmetry 8
2.3.3. Intrinsic p-type behavior 8
2.3.4. Excitonic Effects 9
2.4. Alloying in 2D TMDs 9
2.5. Synthesis of W-based 2D nanomaterials by CVD method 10
2.6. Characterization Techniques for W-Based 2D Nanomaterials 11
2.6.1 Optical Characterization 11
2.6.2 Surface and Morphological Characterization 12
2.7. Summary 12
2.8. References 14
Chapter 3. Role of Quenching in the Growth of WSe2 Monolayer Nanostructures with Salt-Assisted Chemical Vapor Deposition 17
3.1. Introduction 17
3.2. Methods 19
3.2.1. Growth of WSe2 monolayer with CVD 19
3.2.2. Characterization methods 20
3.2.3. Device fabrication 21
3.3. Results and Discussion 22
3.3.1. Growth of WSe2 monolayer flakes without and with thermal quenching 22
3.3.2. Electronic and optoelectronic properties of the CVD-grown WSe2 flakes 30
3.4. Conclusion 33
3.5. References 34
Chapter 4. Tunable Bandgap and Growth Mechanism of WS2xSe2(1-x) Monolayer Alloys Synthesized via Chemical Vapor Deposition 40
4.1. Introduction 40
4.2. Methods 43
4.2.1. Growth of WSSe alloy monolayer with CVD 43
4.2.2. Characterization and device fabrication 44
4.3. Results and Discussion 45
4.4. Conclusion 63
4.5. References 64
Chapter 5. Synthesis of Bilayer WSe2 via Salt-Assisted Chemical Vapor Deposition 71
5.1. Introduction 71
5.2. Experimental Details 74
5.2.1. Growth of bilayer WSe2 using NaCl-assisted CVD 74
5.2.2. Characterization and device fabrication 75
5.3. Results and Discussion 77
5.4. Conclusions 94
5.5. References 95
Chapter 6. Summary and Future Work 101
6.1. Summary 101
6.2. Future Work 103
List of publications 104
