二維異質結構在接面處以凡得瓦力堆疊，有別於三維異質結構共價鍵作為鍵結，卻擁有超快速電荷轉移小於50 fs，並且接面處無懸鍵和無晶格不匹配問題，因此成為近年來熱門研究領域之一。當光通過介電材料時產生建設性干涉或破壞性干涉，會導致材料的吸收和放射增強或衰減，所以多重邊界對於光在材料中所引起的干涉起著關鍵作用，並可以強烈影響元件性能。III-VI族的硒化鎵(Gallium selenide, GaSe)和硒化銦(Indium Selenide, InSe)在少數層皆為直接能隙，並且所形成的異質結構有多色的光響應範圍從紫外光到近紅外光，因此本研究藉由調控二氧化矽的厚度和異質結構的堆疊順序，並且量測InSe/GaSe異質結構和GaSe/InSe異質結構的拉曼光譜和光致發光光譜探討干涉現象對異質結構所造成的影響。根據拉曼光譜和光致發光光譜實驗結果，個別的InSe和GaSe以及接面處的拉曼強度在二氧化矽厚度為270 nm時最強，而InSe和GaSe在接面處下層的拉曼強度比上層強，GaSe接面處下層的發光強度比上層強，並且發現當激發波長接近GaSe能隙時會引發共振現象，導致拉曼強度增強。因此在干涉模型的基礎上，我們提出調控二維InSe/GaSe異質結構和GaSe/InSe異質結構的光子和光電特性的策略，並提升光電元件性能如LED、太陽能電池等提供新的途徑。

The two-dimensional heterostructures are bonded by van der Waals forces at the interface, different from three-dimensional materials which are connected by covalent bonds. These heterostructures lack dangling bonds and lattice mismatch. In addition, ultra-fast charge transfer in van der Waals heterostructures takes place within 50 fs. When incident light passes through the heterostructures, it engages in multiple reflections within the underlying substrates, producing interferences that lead to enhancement or attenuation of Raman intensities and photoluminescence intensities. Thus, the multiple boundaries and thickness of each material play a key role in the interaction of light and heterostructures and strongly affect the device performance. Gallium selenide (GaSe) and indium selenide (InSe) of IIIA-VIA groups have direct band gaps in few layers and multi-color photoresponse ranging from ultraviolet to near infrared. Therefore, in this study, InSe/GaSe and GaSe/InSe heterostructures were fabricated on wafers with silicon dioxide of different thicknesses. The interaction between the light and heterostructures was investigated by employing Raman and photoluminescence spectroscopy. From the results, the Raman intensities of the individual InSe, individual GaSe and junction are the strongest when the thickness of silicon dioxide is 270 nm. The Raman intensities of InSe and GaSe at the lower layer of the junction are higher than the upper layer. The photoluminescence intensity of GaSe at the lower layer of the junction is stronger than the upper layer. It is found that when the excitation wavelength is close to the band gap of GaSe, a resonance phenomenon occur at interface resulting in enhancement of Raman intensities. Based on the interference model, a strategy to modulate the photon and photoelectric properties of InSe/GaSe heterostructures and GaSe/InSe heterostructures is proposed which may provide new ways to improve the performance of optoelectronic devices such as LEDs and solar cells.

論文審定書 i
誌謝 ii
摘要 iii
Abstract iv
圖目錄 viii
表目錄 xii
第一章 緒論 1
1.1前言 1
1.2研究動機 3
1.3二維III-VI族元素層狀半導體硒化鎵和硒化銦簡介 5
1.3.1硒化鎵(Gallium selenide, GaSe) 5
1.3.2硒化銦(Indium selenide, InSe) 6
第二章 理論背景 7
2.1能帶結構 7
2.2拉曼原理 8
2.2.1 InSe和GaSe的聲子色散圖 12
2.2.2 InSe和GaSe的拉曼光譜 15
2.3光致發光光譜原理 17
第三章 實驗儀器和製程步驟 18
3.1儀器介紹 18
3.1.1製程儀器 18
3.1.2測量儀器 19
3.2實驗製程與步驟 20
第四章 實驗結果與討論 22
4.1掃描式光電子能譜顯微儀(Scanning Photoelectron Spectro Microscope, SPEM) 22
4.2退火前異質結構的拉曼光譜和光致發光光譜測量 24
4.2.1不同厚度的二氧化矽與不同堆疊順序的拉曼現象 24
4.2.2不同厚度的二氧化矽和不同堆疊順序的光致發光現象 34
4.2.3異質結構在不同波長的拉曼現象 41
4.3退火後不同疊異質結構的拉曼光譜和光致發光光譜測量 43
4.3.1不同堆疊順序的拉曼現象 43
4.3.2不同堆疊順序的光致發光現象 45
第五章 結論 46
參考文獻 47

1. Novoselov, K.S., et al., Electric field effect in atomically thin carbon films. science, 2004. 306(5696): p. 666-669.
2. Zhang, H., Ultrathin two-dimensional nanomaterials. ACS nano, 2015. 9(10): p. 9451-9469.
3. Zhou, Y., et al., Epitaxy and photoresponse of two-dimensional GaSe crystals on flexible transparent mica sheets. Acs Nano, 2014. 8(2): p. 1485-1490.
4. Geim, A.K. and I.V. Grigorieva, Van der Waals heterostructures. Nature, 2013. 499(7459): p. 419.
5. Peng, B., et al., Ultrafast charge transfer in MoS2/WSe2 p–n Heterojunction. 2D Materials, 2016. 3(2): p. 025020.
6. Hong, X., et al., Ultrafast charge transfer in atomically thin MoS 2/WS 2 heterostructures. Nature nanotechnology, 2014. 9(9): p. 682.
7. Ceballos, F., et al., Ultrafast charge separation and indirect exciton formation in a MoS2–MoSe2 van der Waals heterostructure. ACS nano, 2014. 8(12): p. 12717-12724.
8. Luong, D.H., et al., Tunneling Photocurrent Assisted by Interlayer Excitons in Staggered van der Waals Hetero‐Bilayers. Advanced Materials, 2017. 29(33): p. 1701512.
9. Tongay, S., et al., Tuning interlayer coupling in large-area heterostructures with CVD-grown MoS2 and WS2 monolayers. Nano letters, 2014. 14(6): p. 3185-3190.
10. Dean, C.R., et al., Boron nitride substrates for high-quality graphene electronics. Nature nanotechnology, 2010. 5(10): p. 722.
11. Doan, M.-H., et al., Charge transport in MoS2/WSe2 van der Waals heterostructure with tunable inversion layer. ACS nano, 2017. 11(4): p. 3832-3840.
12. Yu, Y., et al., Equally efficient interlayer exciton relaxation and improved absorption in epitaxial and nonepitaxial MoS2/WS2 heterostructures. Nano letters, 2014. 15(1): p. 486-491.
13. Huo, N., et al., Interlayer coupling and optoelectronic properties of ultrathin two-dimensional heterostructures based on graphene, MoS 2 and WS 2. Journal of Materials Chemistry C, 2015. 3(21): p. 5467-5473.
14. Chen, H., et al., Ultrafast formation of interlayer hot excitons in atomically thin MoS 2/WS 2 heterostructures. Nature communications, 2016. 7: p. 12512.
15. Yan, F., et al., Fast, multicolor photodetection with graphene-contacted p-GaSe/n-InSe van der Waals heterostructures. Nanotechnology, 2017. 28(27): p. 27LT01.
16. Ashkhasi, A., et al. Growth and structural characterizations of GaSe and GaSe: Cd single crystals. in AIP Conference Proceedings. 2017. AIP Publishing.
17. Li, X., et al., Controlled vapor phase growth of single crystalline, two-dimensional GaSe crystals with high photoresponse. Scientific reports, 2014. 4: p. 5497.
18. Lei, S., et al., Synthesis and photoresponse of large GaSe atomic layers. Nano letters, 2013. 13(6): p. 2777-2781.
19. Wu, Y., et al., Simultaneous large continuous band gap tunability and photoluminescence enhancement in GaSe nanosheets via elastic strain engineering. Nano Energy, 2017. 32: p. 157-164.
20. Hu, P., et al., Synthesis of few-layer GaSe nanosheets for high performance photodetectors. ACS nano, 2012. 6(7): p. 5988-5994.
21. Huang, H., et al., Highly sensitive phototransistor based on GaSe nanosheets. Applied Physics Letters, 2015. 107(14): p. 143112.
22. Kou, L., et al., Charging assisted structural phase transitions in monolayer InSe. Physical Chemistry Chemical Physics, 2017. 19(33): p. 22502-22508.
23. Lei, S., et al., Evolution of the electronic band structure and efficient photo-detection in atomic layers of InSe. ACS nano, 2014. 8(2): p. 1263-1272.
24. Sun, Y., et al., InSe: a two-dimensional material with strong interlayer coupling. Nanoscale, 2018. 10(17): p. 7991-7998.
25. Bandurin, D.A., et al., High electron mobility, quantum Hall effect and anomalous optical response in atomically thin InSe. Nature nanotechnology, 2017. 12(3): p. 223.
26. Mudd, G.W., et al., Tuning the bandgap of exfoliated InSe nanosheets by quantum confinement. Advanced Materials, 2013. 25(40): p. 5714-5718.
27. Pandey, T., D.S. Parker, and L. Lindsay, Ab initio phonon thermal transport in monolayer InSe, GaSe, GaS, and alloys. Nanotechnology, 2017. 28(45): p. 455706.
28. Sánchez-Royo, J.F., et al., Electronic structure, optical properties, and lattice dynamics in atomically thin indium selenide flakes. Nano Research, 2014. 7(10): p. 1556-1568.
29. Osman, M., et al., Modulation of opto-electronic properties of InSe thin layers via phase transformation. RSC Advances, 2016. 6(74): p. 70452-70459.
30. Lien, D.-H., et al., Engineering light outcoupling in 2D materials. Nano letters, 2015. 15(2): p. 1356-1361.
31. Chen, Z., J. Biscaras, and A. Shukla, Optimal light harvesting in 2D semiconductor heterostructures. 2D Materials, 2017. 4(2): p. 025115.
32. Srour, J., et al., Comparative study of structural and electronic properties of GaSe and InSe polytypes. arXiv preprint arXiv:1803.08158, 2018.