近年來，半導體微縮製程的極限，使其朝向改變閘極結構或開發新的通道材料發展，因此，人們對二維材料的研究開始興起，近期，屬於過渡金屬硫屬化合物且具有扭曲1T’結構的二硫化錸(ReS2)由於其有趣的光學和電子特性而引起了人們的關注。迄今為止，已經有許多對於ReS2的能帶結構以及電流特性的研究，但對於發光特性的了解還不夠透徹。
因此，本論文藉由不同環境溫度下，量測的ReS2光致發光，確定其適合在低溫的環境下工作，並在低溫中量測ReS2 PL的偏振依賴性，研究了不同激子峰的發射是由於不同晶格方向的電子-電洞對複合所產生，而材料照光吸收的部分，受到晶格結構各向異性的特點，對於沿Re-Re金屬鍵方向偏振的光吸收較率較高。接著，透過轉移矩陣法結合ReS2激子的特性來對照光致發光激發(PLE)的實驗，發現了在發射光譜中，多個激子發射峰的出現，是由於光子被限制在ReS2材料內部，造成極化子與激子的耦合，導致主要的兩個激子峰分裂，而ReS2材料厚度發生變化時，相當於共振腔光子模態改變，會使吸收光譜受到影響，因而對於不同波長光源激發展現出相異的特性。
這些發現促進了對於ReS2的光致發光光學性質的理解，有利於未來位於近紅外波段，具有偏振特性的新穎奈米電子元件開發，並可延伸至其他二維材料進行異質結構的整合。

ReS2 which owns the exotic optical and electrical properties has attracted great attentions. Currently, multiple works have theoretically investigated its electronic band structure and experimentally explored its electrical transport properties. But the luminescence characteristics of ReS2 remains largely unexplored. In this thesis, we perform polarization resolved photoluminescence measurements on ReS2 at cryogenic temperature. Our result reveals multiple excitonic peaks, which are originated from the recombination of electron-hole pairs in different lattice directions (anisotropic crystal structure of ReS2). In addition, we observe that the exciton peaks measured from the thicker ReS2 flakes could exhibit the splitting behaviors. Our numerical simulation (transfer matrix method) together with the photoluminescence excitation (PLE) experiments indicate that the splitting is caused by the coupling between polarons and excitons. Critically, our results not only show the evidence of strong light-matter coupling of ReS2, but also suggest its usefulness to novel nanophotonics applications.

[1] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Grigorieva, and A. A. Firsov, "Electric field effect in atomically thin carbon films," Science, vol. 306, no. 5696, pp. 666-669, 2004.
[2] P. Ajayan, P. Kim, and K. Banerjee, "Two-dimensional van der Waals materials," Physics Today, vol. 69, no. 9, pp. 39-44, 2016.
[3] Sujay B Desai, Gyungseon Seol, Jeong Seuk Kang, Hui Fang, Corsin Battaglia, Rehan Kapadia, Joel W Ager, Jing Guo, and Ali Javey, "Strain-induced indirect to direct bandgap transition in multilayer WSe2," Nano letters, vol. 14, no. 8, pp. 4592-4597, 2014.
[4] J. N. Huang, T. B. Hoang, and M. H. Mikkelsen, "Probing the origin of excitonic states in monolayer WSe2," Scientific Reports, vol. 6, 2016, Art no. 22414.
[5] Chenhao Jin, Emma C Regan, Aiming Yan, M Iqbal Bakti Utama, Danqing Wang, Sihan Zhao, Ying Qin, Sijie Yang, Zhiren Zheng, and Shenyang Shi, "Observation of moiré excitons in WSe2/WS2 heterostructure superlattices," Nature, vol. 567, no. 7746, pp. 76-80, 2019.
[6] Aaron M Jones, Hongyi Yu, Nirmal J Ghimire, Sanfeng Wu, Grant Aivazian, Jason S Ross, Bo Zhao, Jiaqiang Yan, David G Mandrus, and Di Xiao, "Optical generation of excitonic valley coherence in monolayer WSe2," Nature nanotechnology, vol. 8, no. 9, pp. 634-638, 2013.
[7] Jason S Ross, Philip Klement, Aaron M Jones, Nirmal J Ghimire, Jiaqiang Yan, DG Mandrus, Takashi Taniguchi, Kenji Watanabe, Kenji Kitamura, and Wang Yao, "Electrically tunable excitonic light-emitting diodes based on monolayer WSe2 p–n junctions," Nature nanotechnology, vol. 9, no. 4, pp. 268-272, 2014.
[8] Ajit Srivastava, Meinrad Sidler, Adrien V Allain, Dominik S Lembke, Andras Kis, and A Imamoğlu, "Valley Zeeman effect in elementary optical excitations of monolayer WSe2," Nature Physics, vol. 11, no. 2, pp. 141-147, 2015.
[9] A. Varghese, D. Saha, K. Thakar, V. Jindal, S. Ghosh, N. V. Medhekar, S. Ghosh, and S. Lodha, "Near-Direct Bandgap WSe2/ReS2 Type-II pn Heterojunction for Enhanced Ultrafast Photodetection and High-Performance Photovoltaics," Nano Letters, vol. 20, no. 3, pp. 1707-1717, 2020.
[10] Weijie Zhao, Zohreh Ghorannevis, Leiqiang Chu, Minglin Toh, Christian Kloc, Ping-Heng Tan, and Goki Eda, "Evolution of electronic structure in atomically thin sheets of WS2 and WSe2," ACS nano, vol. 7, no. 1, pp. 791-797, 2013.
[11] Ming-Hui Chiu, Ming-Yang Li, Wengjing Zhang, Wei-Ting Hsu, Wen-Hao Chang, Mauricio Terrones, Humberto Terrones, and Lain-Jong Li, "Spectroscopic Signatures for Interlayer Coupling in MoS2–WSe2 van der Waals Stacking," ACS Nano, vol. 8, no. 9, pp. 9649-9656, 2014.
[12] Ming-Yang Li, Yumeng Shi, Chia-Chin Cheng, Li-Syuan Lu, Yung-Chang Lin, Hao-Lin Tang, Meng-Lin Tsai, Chih-Wei Chu, Kung-Hwa Wei, and Jr-Hau He, "Epitaxial growth of a monolayer WSe2-MoS2 lateral pn junction with an atomically sharp interface," Science, vol. 349, no. 6247, pp. 524-528, 2015.
[13] Matin Amani, Der-Hsien Lien, Daisuke Kiriya, Jun Xiao, Angelica Azcatl, Jiyoung Noh, Surabhi R Madhvapathy, Rafik Addou, Santosh Kc, and Madan Dubey, "Near-unity photoluminescence quantum yield in MoS2," Science, vol. 350, no. 6264, pp. 1065-1068, 2015.
[14] Jason W Christopher, Bennett B Goldberg, and Anna K Swan, "Long tailed trions in monolayer MoS2: Temperature dependent asymmetry and resulting red-shift of trion photoluminescence spectra," Scientific reports, vol. 7, no. 1, pp. 1-8, 2017.
[15] Xu Cui, Gwan-Hyoung Lee, Young Duck Kim, Ghidewon Arefe, Pinshane Y Huang, Chul-Ho Lee, Daniel A Chenet, Xian Zhang, Lei Wang, and Fan Ye, "Multi-terminal transport measurements of MoS2 using a van der Waals heterostructure device platform," Nature nanotechnology, vol. 10, no. 6, pp. 534-540, 2015.
[16] Oriol Lopez-Sanchez, Dominik Lembke, Metin Kayci, Aleksandra Radenovic, and Andras Kis, "Ultrasensitive photodetectors based on monolayer MoS2," Nature nanotechnology, vol. 8, no. 7, pp. 497-501, 2013.
[17] Kin Fai Mak, Keliang He, Jie Shan, and Tony F Heinz, "Control of valley polarization in monolayer MoS2 by optical helicity," Nature nanotechnology, vol. 7, no. 8, pp. 494-498, 2012.
[18] B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, "Single-layer MoS2 transistors," Nature Nanotechnology, vol. 6, no. 3, pp. 147-150, 2011.
[19] Hualing Zeng, Junfeng Dai, Wang Yao, Di Xiao, and Xiaodong Cui, "Valley polarization in MoS2 monolayers by optical pumping," Nature nanotechnology, vol. 7, no. 8, pp. 490-493, 2012.
[20] Burak Aslan, Daniel A. Chenet, Arend M. van der Zande, James C. Hone, and Tony F. Heinz, "Linearly Polarized Excitons in Single- and Few-Layer ReS2 Crystals," ACS Photonics, vol. 3, no. 1, pp. 96-101, 2016.
[21] Rahul Gogna, Long Zhang, and Hui Deng, "Self-Hybridized, Polarized Polaritons in ReS2 Crystals," ACS Photonics, vol. 7, no. 12, pp. 3328-3332, 2020.
[22] Lingli Huang, Fangyuan Zheng, Honglin Chen, Quoc Huy Thi, Xin Chen, Haijun Liu, Chun-Sing Lee, Qingming Deng, Jiong Zhao, and Thuc Hue Ly, "Mechanical origin of martensite-like structures in two-dimensional ReS2," Communications Materials, vol. 2, no. 1, p. 87, 2021.
[23] J. Jadczak, J. Kutrowska-Girzycka, T. Smolenski, P. Kossacki, Y. S. Huang, and L. Bryja, "Exciton binding energy and hydrogenic Rydberg series in layered ReS2," Scientific Reports, vol. 9, 2019, Art no. 1578.
[24] Erfu Liu, Yajun Fu, Yaojia Wang, Yanqing Feng, Huimei Liu, Xiangang Wan, Wei Zhou, Baigeng Wang, Lubin Shao, Ching-Hwa Ho, Ying-Sheng Huang, Zhengyi Cao, Laiguo Wang, Aidong Li, Junwen Zeng, Fengqi Song, Xinran Wang, Yi Shi, Hongtao Yuan, Harold Y. Hwang, Yi Cui, Feng Miao, and Dingyu Xing, "Integrated digital inverters based on two-dimensional anisotropic ReS2 field-effect transistors," Nature Communications, vol. 6, no. 1, p. 6991, 2015.
[25] X. H. Meng, Y. J. Zhou, K. Chen, R. H. Roberts, W. Z. Wu, J. F. Lin, R. T. Chen, X. C. Xu, and Y. G. Wang, "Anisotropic Saturable and Excited-State Absorption in Bulk ReS2," Advanced Optical Materials, vol. 6, no. 14, 2018, Art no. 1800137.
[26] N. B. Mohamed, K. Shinokita, X. F. Wang, H. E. Lim, D. Z. Tan, Y. Miyauchi, and K. Matsuda, "Photoluminescence quantum yields for atomically thin-layered ReS2: Identification of indirect-bandgap semiconductors," Applied Physics Letters, vol. 113, no. 12, 2018, Art no. 121112.
[27] M. Rahman, K. Davey, and S. Z. Qiao, "Advent of 2D Rhenium Disulfide (ReS2): Fundamentals to Applications," Advanced Functional Materials, vol. 27, no. 10, 2017, Art no. 1606129.
[28] S. Sim, D. Lee, M. Noh, S. Cha, C. H. Soh, J. H. Sung, M. H. Jo, and H. Choi, "Selectively tunable optical Stark effect of anisotropic excitons in atomically thin ReS2," Nature Communications, vol. 7, 2016, Art no. 13569.
[29] J. Y. Wang, Y. J. Zhou, D. Xiang, S. J. Ng, K. Watanabe, T. Taniguchi, and G. Eda, "Polarized Light-Emitting Diodes Based on Anisotropic Excitons in Few-Layer ReS2," Advanced Materials, vol. 32, no. 32, 2020, Art no. 2001890.
[30] X. F. Wang, K. Shinokita, H. E. Lim, N. B. Mohamed, Y. Miyauchi, N. T. Cuong, S. Okada, and K. Matsuda, "Direct and Indirect Exciton Dynamics in Few-Layered ReS2 Revealed by Photoluminescence and Pump-Probe Spectroscopy," Advanced Functional Materials, vol. 29, no. 6, 2019, Art no. 1806169.
[31] Maksym Sich, Dmitry V Skryabin, and Dmitry N Krizhanovskii, "Soliton physics with semiconductor exciton–polaritons in confined systems," Comptes Rendus Physique, vol. 17, no. 8, pp. 908-919, 2016.