Study 2D magnetic materials by Raman spectroscopy
- 발행기관 서강대학교 일반대학원
- 지도교수 정현식
- 발행년도 2025
- 학위수여년월 2025. 8
- 학위명 박사
- 학과 및 전공 일반대학원 물리학과
- 실제 URI http://www.dcollection.net/handler/sogang/000000081716
- UCI I804:11029-000000081716
- 본문언어 영어
- 저작권 서강대학교 논문은 저작권 보호를 받습니다.
초록 (요약문)
Two-dimensional magnetic materials have attracted much interest owing to their diverse and interesting properties for electronic and spintronic applications. For examples, CrPS4, which is an A-type antiferromagnetic, shows a Fano resonance in the photoluminescence (PL) spectrum, and NiPS3, which is an XXZ- type antiferromagnetic, shows an extremely sharp PL signal and magnons in the Raman spectrum. On the other hands, Raman spectroscopy is a powerful tool to investigate the van der Waals materials and used to determine, e.g., the thickness, stacking order, and the interlayer interaction. In this thesis, lattice vibrations in vdW magnetic materials and the heterostructures including a magnetic material were investigated carefully by polarized Raman spectroscopy. We studied the temperature dependence of Raman spectrum of CrPS4, the thickness dependent Raman spectra of few-layer NiPS3, and the Raman spectra of 1L-MoS2/nL-NiPS3 heterostructures. In the first study, the Raman spectra were measured down to the bilayer, and correlations of Raman signal with the resonance effect and the magnetic phase transition were studied. In the second work, the thickness of few-layer NiPS3 was determined by the low- frequency breathing and shear modes, and the Davydov splitting of the mode at ~255 cm–1. In the last work on 1L-MoS2/nL-NiPS3 heterostructures, the interlayer vibrational modes can be described well with the linear chain model analysis. On the other hands, the behavior of the magnon suggest a complicated interlayer interaction between the two materials.
more목차
Abstract 10
I. Introduction 11
II. Background 15
1. Raman spectroscopy 15
2. Chromium thiophosphate (CrPS4) 19
3. Nickel phosphorous trichalcogenides (NiPS3) 23
4. Molybdenum disulfide (MoS2) 27
5. Second-Harmonic Generation(SHG) 30
III. Experiments 33
1. Sample preparation 33
2. Raman measurement 36
3. Polarized Second-Harmonic Generation (SHG) measurements 38
IV. Results and Discussions 39
1. The temperature dependence of Raman spectrum of antiferromagnetic
CrPS4 39
1.1. Polarized Raman spectra of CrPS4 39
1.2. Temperature dependent Raman spectrum of CrPS4 45
1.3. Raman spectra of few-layer CrPS4 48
1.4. Summary 62
2. Thickness dependence of Raman spectra of few-layer anti-
ferromagnetic NiPS3 64
2.1. Low–frequency Raman spectrum of NiPS3 64
2.2. High-frequency Raman spectrum of NiPS3 67
2.3. Dependence on Excitation Energy and Temperature 71
2.4. Linear chain model for Raman modes of NiPS3 73
2.5. Summary 80
3. Raman spectrum of 1L-MoS2/nL-NiPS3 heterostructures 81
3.1. Low-frequency Raman spectra of 1L-MoS2/nL-NiPS3 81
3.2. High-frequency Raman spectra of 1L-MoS2/nL-NiPS3 83
3.3. The twist angle dependence of the heterostructures 86
3.4. Temperature dependence of 1L-MoS2/nL-NiPS3 heterostructures
95
3.5. Summary 98
V. Conclusion 99
VI. References 100
