過渡金屬硫族化合物具有特殊的能帶結構、強自旋軌域耦合特性，在元件表現上有獨特的光學與電學特性，受到國際高度重視。本論文主要藉由化學氣相沉積法合成二硒化鎢與相異二維半導體材料之異質結構並探討製程參數對二硒化鎢合成的成長行為。以二硒化鎢成長行為的研究為基礎，提出一階段製程與二階段製程合成過渡金屬硫族化合物異質結構，如二硒化鉬/二硒化鎢，二硒化鎢/二硫化鉬等，並製備成下閘級式場效電晶體，探討其電學性質，其中二硒化鎢呈現雙級性半導體特性，二硒化鎢/二硫化鉬異質結構具有整流特性。最後，探討過渡金屬硫族化合物在不同工作氣氛下的材料穩定度，以實現二維半導體異質結構之生長。

Transition metal dichalcogenides (TMDc) have attracted attention due to unique band structure and spin valley coupling for electronics and optoelectronics. In this research, tungsten diselenides (WSe2) and TMDc heterostructures were synthesized by chemical vapor deposition. Based on the study of WSe2 growth behavior, we developed the one-step process and two-step process to synthesize TMDc heterostructures, such as MoSe2/WSe2 and WSe2/MoS2. In addition, we report the fabrication of back-gate field effect transistors based on WSe2 and TMDc heterostructures. The WSe2 transistor demonstrated ambipolar operation, and WSe2/MoS2 heterostructures displayed rectifying characteristic. Finally, to achieve the growth of the varying TMDc heterostructures, we discussed the stability of the TMDc materials in different working atmosphere

1. Novoselov, K.S., et al., Electric Field Effect in Atomically Thin Carbon Films. Science, 2004. 306(5696): p. 666-669.
2. Mak, K.F., et al., Atomically Thin MoS2: A New Direct-Gap Semiconductor. Physical Review Letters, 2010. 105(13): p. 136805.
3. Wilson, J.A., F.J. Di Salvo, and S. Mahajan, Charge-Density Waves in Metallic, Layered, Transition-Metal Dichalcogenides. Physical Review Letters, 1974. 32(16): p. 882-885.
4. Salvatore, G.A., et al., Fabrication and Transfer of Flexible Few-Layers MoS2 Thin Film Transistors to Any Arbitrary Substrate. ACS Nano, 2013. 7(10): p. 8809-8815.
5. Podzorov, V., et al., High-mobility field-effect transistors based on transition metal dichalcogenides. Applied Physics Letters, 2004. 84(17): p. 3301-3303.
6. Chhowalla, M., et al., The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets. Nat Chem, 2013. 5(4): p. 263-275.
7. Kappera, R., et al., Phase-engineered low-resistance contacts for ultrathin MoS2 transistors. Nat Mater, 2014. 13(12): p. 1128-1134.
8. Zhao, W., et al., Origin of Indirect Optical Transitions in Few-Layer MoS2, WS2, and WSe2. Nano Letters, 2013. 13(11): p. 5627-5634.
9. Huang, W., et al., Theoretical study of thermoelectric properties of few-layer MoS2 and WSe2. Physical Chemistry Chemical Physics, 2014. 16(22): p. 10866-10874.
10. Chang, J., L.F. Register, and S.K. Banerjee, Ballistic performance comparison of monolayer transition metal dichalcogenide MX2 (M = Mo, W; X = S, Se, Te) metal-oxide-semiconductor field effect transistors. Journal of Applied Physics, 2014. 115(8): p. 084506.
11. Zeng, H., et al., Optical signature of symmetry variations and spin-valley coupling in atomically thin tungsten dichalcogenides. Scientific Reports, 2013. 3: p. 1608.
12. RadisavljevicB, et al., Single-layer MoS2 transistors. Nat Nano, 2011. 6(3): p. 147-150.
13. Liu, J., et al., Ultrafast Self-Limited Growth of Strictly Monolayer WSe2 Crystals. Small, 2016. 12(41): p. 5741-5749.
14. Fang, H., et al., High-Performance Single Layered WSe2 p-FETs with Chemically Doped Contacts. Nano Letters, 2012. 12(7): p. 3788-3792.
15. Lopez-Sanchez, O., et al., Ultrasensitive photodetectors based on monolayer MoS2. Nat Nano, 2013. 8(7): p. 497-501.
16. Zhang, W., et al., High-Gain Phototransistors Based on a CVD MoS2 Monolayer. Advanced Materials, 2013. 25(25): p. 3456-3461.
17. Baugher, B.W.H., et al., Optoelectronic devices based on electrically tunable p-n diodes in a monolayer dichalcogenide. Nat Nano, 2014. 9(4): p. 262-267.
18. Geim, A.K. and I.V. Grigorieva, Van der Waals heterostructures. Nature, 2013. 499(7459): p. 419-425.
19. Zhang, X.-Q., et al., Synthesis of Lateral Heterostructures of Semiconducting Atomic Layers. Nano Letters, 2015. 15(1): p. 410-415.
20. Tan, C. and H. Zhang, Epitaxial Growth of Hetero-Nanostructures Based on Ultrathin Two-Dimensional Nanosheets. Journal of the American Chemical Society, 2015. 137(38): p. 12162-12174.
21. Huang, C., et al., Lateral heterojunctions within monolayer MoSe2–WSe2 semiconductors. Nat Mater, 2014. 13(12): p. 1096-1101.
22. Duan, X., et al., Lateral epitaxial growth of two-dimensional layered semiconductor heterojunctions. Nat Nano, 2014. 9(12): p. 1024-1030.
23. Tsai, M.-L., et al., High-efficiency omnidirectional photoresponses based on monolayer lateral p-n heterojunctions. Nanoscale Horizons, 2017. 2(1): p. 37-42.
24. Chen, J., et al., Chemical Vapor Deposition of Large-Sized Hexagonal WSe2 Crystals on Dielectric Substrates. Advanced Materials, 2015. 27(42): p. 6722-6727.
25. Agnihotri, O.P., H.K. Sehgal, and A.K. Garg, Laser excited Raman spectra of Gr. VI semiconducting compounds. Solid State Communications, 1973. 12(2): p. 135-138.
26. Huang, J., et al., Large-area synthesis of monolayer WSe2 on a SiO2/Si substrate and its device applications. Nanoscale, 2015. 7(9): p. 4193-4198.
27. Huang, J.-K., et al., Large-Area Synthesis of Highly Crystalline WSe2 Monolayers and Device Applications. ACS Nano, 2014. 8(1): p. 923-930.
28. Li, H., et al., Mechanical Exfoliation and Characterization of Single- and Few-Layer Nanosheets of WSe2, TaS2, and TaSe2. Small, 2013. 9(11): p. 1974-1981.
29. Lee, C., et al., Anomalous Lattice Vibrations of Single- and Few-Layer MoS2. ACS Nano, 2010. 4(5): p. 2695-2700.
30. Li, H., et al., Preparation and Applications of Mechanically Exfoliated Single-Layer and Multilayer MoS2 and WSe2 Nanosheets. Accounts of Chemical Research, 2014. 47(4): p. 1067-1075.
31. Zhou, H., et al., Large Area Growth and Electrical Properties of p-Type WSe2 Atomic Layers. Nano Letters, 2015. 15(1): p. 709-713.
32. Kai, X., et al., Atomic-layer triangular WSe 2 sheets: synthesis and layer-dependent photoluminescence property. Nanotechnology, 2013. 24(46): p. 465705.
33. Wu, S., et al., Vapor–Solid Growth of High Optical Quality MoS2 Monolayers with Near-Unity Valley Polarization. ACS Nano, 2013. 7(3): p. 2768-2772.
34. Li, S., et al., Halide-assisted atmospheric pressure growth of large WSe2 and WS2 monolayer crystals. Applied Materials Today, 2015. 1(1): p. 60-66.
35. Liu, B., et al., Chemical Vapor Deposition Growth of Monolayer WSe2 with Tunable Device Characteristics and Growth Mechanism Study. ACS Nano, 2015. 9(6): p. 6119-6127.
36. Sarah, M.E., et al., Controlling nucleation of monolayer WSe 2 during metal-organic chemical vapor deposition growth. 2D Materials, 2016. 3(2): p. 025015.
37. Lee, Y.-H., et al., Synthesis of Large-Area MoS2 Atomic Layers with Chemical Vapor Deposition. Advanced Materials, 2012. 24(17): p. 2320-2325.
38. Ling, X., et al., Role of the Seeding Promoter in MoS2 Growth by Chemical Vapor Deposition. Nano Letters, 2014. 14(2): p. 464-472.
39. Lee, Y.-H., et al., Synthesis and Transfer of Single-Layer Transition Metal Disulfides on Diverse Surfaces. Nano Letters, 2013. 13(4): p. 1852-1857.
40. Chen, K., et al., Lateral Built-In Potential of Monolayer MoS2–WS2 In-Plane Heterostructures by a Shortcut Growth Strategy. Advanced Materials, 2015. 27(41): p. 6431-6437.
41. Chen, K., et al., Electronic Properties of MoS2–WS2 Heterostructures Synthesized with Two-Step Lateral Epitaxial Strategy. ACS Nano, 2015. 9(10): p. 9868-9876.
42. Gong, Y., et al., Two-Step Growth of Two-Dimensional WSe2/MoSe2 Heterostructures. Nano Letters, 2015. 15(9): p. 6135-6141.
43. Heo, H., et al., Rotation-Misfit-Free Heteroepitaxial Stacking and Stitching Growth of Hexagonal Transition-Metal Dichalcogenide Monolayers by Nucleation Kinetics Controls. Advanced Materials, 2015. 27(25): p. 3803-3810.
44. Bogaert, K., et al., Diffusion-Mediated Synthesis of MoS2/WS2 Lateral Heterostructures. Nano Letters, 2016. 16(8): p. 5129-5134.
45. Li, M.-Y., et al., Epitaxial growth of a monolayer WSe2-MoS2 lateral p-n junction with an atomically sharp interface. Science, 2015. 349(6247): p. 524.
46. Mahjouri-Samani, M., et al., Patterned arrays of lateral heterojunctions within monolayer two-dimensional semiconductors. Nature Communications, 2015. 6: p. 7749.
47. Elías, A.L., et al., Controlled Synthesis and Transfer of Large-Area WS2 Sheets: From Single Layer to Few Layers. ACS Nano, 2013. 7(6): p. 5235-5242.
48. Zhang, W., et al., Ultrahigh-Gain Photodetectors Based on Atomically Thin Graphene-MoS2 Heterostructures. Scientific Reports, 2014. 4: p. 3826.
49. Lin, Y.-C., et al., Atomically Thin Heterostructures Based on Single-Layer Tungsten Diselenide and Graphene. Nano Letters, 2014. 14(12): p. 6936-6941.
50. Wang, S., X. Wang, and J.H. Warner, All Chemical Vapor Deposition Growth of MoS2:h-BN Vertical van der Waals Heterostructures. ACS Nano, 2015. 9(5): p. 5246-5254.
51. Gong, Y., et al., Vertical and in-plane heterostructures from WS2/MoS2 monolayers. Nat Mater, 2014. 13(12): p. 1135-1142.
52. Samad, L., et al., Layer-Controlled Chemical Vapor Deposition Growth of MoS2 Vertical Heterostructures via van der Waals Epitaxy. ACS Nano, 2016. 10(7): p. 7039-7046.
53. Chen, L., et al., Screw-Dislocation-Driven Growth of Two-Dimensional Few-Layer and Pyramid-like WSe2 by Sulfur-Assisted Chemical Vapor Deposition. ACS Nano, 2014. 8(11): p. 11543-11551.
54. Shaw, J.C., et al., Chemical vapor deposition growth of monolayer MoSe2 nanosheets. Nano Research, 2014. 7(4): p. 511-517.
55. Zhang, Y., et al., Controlled Growth of High-Quality Monolayer WS2 Layers on Sapphire and Imaging Its Grain Boundary. ACS Nano, 2013. 7(10): p. 8963-8971.
56. Chen, L., et al., Step-Edge-Guided Nucleation and Growth of Aligned WSe2 on Sapphire via a Layer-over-Layer Growth Mode. ACS Nano, 2015. 9(8): p. 8368-8375.
57. Cain, J.D., et al., Growth Mechanism of Transition Metal Dichalcogenide Monolayers: The Role of Self-Seeding Fullerene Nuclei. ACS Nano, 2016. 10(5): p. 5440-5445.
58. Li, B., et al., Solid–Vapor Reaction Growth of Transition-Metal Dichalcogenide Monolayers. Angewandte Chemie International Edition, 2016. 55(36): p. 10656-10661.
59. Cao, D., et al., Role of Chemical Potential in Flake Shape and Edge Properties of Monolayer MoS2. The Journal of Physical Chemistry C, 2015. 119(8): p. 4294-4301.
60. Bosi, M., Growth and synthesis of mono and few-layers transition metal dichalcogenides by vapour techniques: a review. RSC Advances, 2015. 5(92): p. 75500-75518.
61. Li, H., et al., Laterally Stitched Heterostructures of Transition Metal Dichalcogenide: Chemical Vapor Deposition Growth on Lithographically Patterned Area. ACS Nano, 2016. 10(11): p. 10516-10523.
62. Jones, A.M., et al., Optical generation of excitonic valley coherence in monolayer WSe2. Nat Nano, 2013. 8(9): p. 634-638.
63. You, Y., et al., Observation of biexcitons in monolayer WSe2. Nat Phys, 2015. 11(6): p. 477-481.
64. Wang, G., et al., Valley dynamics probed through charged and neutral exciton emission in monolayer ${\mathrm{WSe}}_{2}$. Physical Review B, 2014. 90(7): p. 075413.
65. Krivanek, O.L., et al., Atom-by-atom structural and chemical analysis by annular dark-field electron microscopy. Nature, 2010. 464(7288): p. 571-574.
66. Levendorf, M.P., et al., Graphene and boron nitride lateral heterostructures for atomically thin circuitry. Nature, 2012. 488(7413): p. 627-632.
67. Liu, Z., et al., In-plane heterostructures of graphene and hexagonal boron nitride with controlled domain sizes. Nat Nano, 2013. 8(2): p. 119-124.
68. Liu, L., et al., Heteroepitaxial Growth of Two-Dimensional Hexagonal Boron Nitride Templated by Graphene Edges. Science, 2014. 343(6167): p. 163-167.
69. Wu, J., et al., Layer Thinning and Etching of Mechanically Exfoliated MoS2 Nanosheets by Thermal Annealing in Air. Small, 2013. 9(19): p. 3314-3319.
70. Yamamoto, M., et al., Self-Limiting Layer-by-Layer Oxidation of Atomically Thin WSe2. Nano Letters, 2015. 15(3): p. 2067-2073.
71. Ionescu, R., et al., Oxygen etching of thick MoS2 films. Chemical Communications, 2014. 50(76): p. 11226-11229.