서강대학교

목차

I. Introduction 1
II. Theory 6
A. Transition Metal Dichalcogenides (TMDs) 6
B. Tungsten Disulfide (WS2) 7
C. Tungsten Diselenide (WSe2) 9
III. Experiments 11
A. Sample Fabrication 11
(1) Sample transfer 11
(2) AFM cleaning 12
B. Raman Spectroscopy 13
C. Photoluminescence 15
D. Second Harmonic Generation 16
E. Selected Area Electron Diffraction[31] 18
F. Chemical Vapor Deposition[32, 33] 20
IV. Results & Discussion 22
A. Determinization and categorization of twist angle 22
(1) Determinization and categorization of exfoliated heterostructure’s twist
angle 22
(2) Fabrication of CVD-grown 1L-WS2/1L-WSe2 heterostructure and
determination of its twist angle 25
B. Low-frequency Raman signal of 1L-WS2/1L-WSe2 heterostructure 27
(1) Low-frequency Raman signal of the CVD-grown 1L-WS2/1L-WSe2
heterostructure 27
(2) Low-frequency Raman signal of the exfoliated 1L-WS2/1L-WSe2
heterostructure 30
C. SAED and PL measurements 31
(1) Fabrication of heterostructures on TEM membrane 31
(2) Polarized SHG signal of heterostructures on TEM membrane 33
(3) Stacking configurations of two heterostructures with slight differences of
twist angle 34
(4) TEM measurement of heterostructures 35
(5) PL measurement of heterostructures 37
D. Low-frequency Raman mapping. 39
V. Summary 42
VI. References 43