本論文使用化學氣相傳導法合成層狀過渡金屬硫化物ReS2-xSex (x = 0, 1, 2)，並將其製作成光感測元件，透過化學氣相傳導法能夠合成出不同比例之 ReS2-xSex，使用拉曼光譜儀分析其晶格振動模態變化以及光激發螢光光譜儀觀察其能隙變化，X光光電子能譜儀以及X光能量散射光譜儀測定成分組成，結果顯示ReS2-xSex可以有效地利用莫耳數比計算控制其比例。首先將ReS2-xSex製作成金屬-半導體-金屬光感測器元件，進行電性量測，確保樣品為歐姆接觸，再來使用405、532、633以及808 nm四種不同波長的雷射量測光電流，不同波長造成的光子能量所產生的光電流量與樣品本身的吸光度與吸收效率有關，在這四種雷射中，波長越短所產生的光響應度反應最佳，而波長越長的光響應度反應則越差，由於能隙的不同，ReSe2 (1.29 eV) 的能隙較ReS2 (1.51 eV) 小，其光吸收度較佳，使得在光響應度上擁有較佳的表現，而ReSSe受限於其合金結構所導致的載子散射，造成其光電導率大幅度降低，為三種組成中最低。歸一化光響應度與載子遷移率、載子活期和量子轉換效率有關，從實驗中可得知載子活期為影響歸一化光響應度的最主要因素。

In this thesis, we used chemical vapor transport method to synthesize layered transition metal dichalcogenides ReS2-xSex (x = 0, 1, 2) single crystals. The lattice vibration of ReS2-xSex was investigated by Raman spectroscopy. The band gap structure was demonstrated by photoluminescence (PL). The composition of ReS2-xSex was confirmed by X-ray photoelectron spectroscopy (XPS) and Energy dispersive X-ray spectroscopy (EDX). The results of XPS and EDX showed that the composition of ReS2-xSex could be tunable by calculating the mole number ratio of the starting material. We fabricated ReS2-xSex into metal-semiconductor-metal photodetector device and demonstrated photocurrent properties under different wavelength of laser sources, which were 405, 532, 633 and 808 nm. Different photon energy and absorbance could be generated from different laser source. Within 4 lasers, the shorter wavelength exhibited better photoresponse than the longer ones. ReSe2 showed greater light absorption and photoresponse due to the smaller energy gap than ReS2. ReSSe demonstrated relatively low photoconductivity and photoresponsivity. This could be caused by alloying-induced carrier scattering. We discovered that ReS2-xSex has the best photoresponse under the illumination of 405 nm laser source. From the results, we inferred that the carrier lifetime was the most important factor affecting the normalized photoresponsivity.

[1] K. I. Bolotin, K. J. Sikes, Z. Jiang, M. Klima, G. Fudenberg, J. Hone, P. Kim, and H. L. Stormer, "Ultrahigh electron mobility in suspended graphene,” Solid State Commun., vol. 146, pp. 351-355, 2008.
[2] F. Bonaccorso, Z. Sun, T. Hasan, and A. C. Ferrari, “Graphene photonics and optoelectronics,” Nature Photon., vol. 4, pp. 611-622, 2010.
[3] F. Schwierz, “Graphene transistors,” Nature Nanotech., vol. 5, pp. 487-496, 2010.
[4] X. Li, Y. Zhu, W. Cai, M. Borysiak, B. Han, D. Chen, R. D. Piner, L. Colomba, and R. S. Ruoff, “Transfer of large-area graphene films for high-performance transparent conductive electrodes,” Nano Lett., vol. 9, pp. 4359-4363, 2009.
[5] V. M. Pereira and A. H. C. Neto, “Strain engineering of graphene's electronic structure,” Phys. Rev. Lett., vol. 103, 2009.
[6] D. Wei, Y. Liu, Y. Wang, H. Zhang, L. Huang, and G. Yu, “Synthesis of n-doped graphene by chemical vapor deposition and its electrical properties,” Nano Lett., vol. 9, pp. 1752-1758, 2009.
[7] Y. Zhu, S. Murali, W. Cai, X. Li, J. W. Suk, J. R. Potts, and R. S. Ruoff, “Graphene and graphene oxide: synthesis, properties, and applications,” Adv. Mater., vol. 22, pp. 3906-3924, 2010.
[8] W. Jaegermann and H. Tributsch, “Interfacial properties of semiconducting transition metal chalcogenides,” Progress Surf. Sci., vol. 29, pp. 1-167, 1988.
[9] W. J. Yu, Y. Liu, H. Zhou, A. Lin, Z. Li, Y. Huang, and X. Duan, “Highly efficient gate-tunable photocurrent generation in vertical heterostructures of layered materials,” Nature Nanotech., vol. 8, pp. 952-958, 2013.
[10] H. Li, J. Wu, Z. Yin, and H. Zhang, “Preparation and applications of mechanically exfoliated single-layer and multilayer MoS2 and WSe2 nanosheets,” Acc. Chem. Res., vol. 47, pp. 1067-1075, 2014.
[11] N. Liu, P. Kim, J. H. Kim, J. H. Ye, S. Kim, and C. J. Lee, “Large-area atomically thin MoS2 nanosheets prepared using electrochemical exfoliation,” ACS Nano., vol. 8, pp. 6902-6910, 2014.
[12] G. Prasad and O. N. Srivastava, “The high-efficiency (17.1%) WSe2 photo-electrochemical solar cell,” J. Phys. D: Appl. Phys., vol. 21, pp. 1028-1030, 1988.
[13] S. Min and G. Lu, “Sites for high efficient photocatalytic hydrogen evolution on a limited-layered MoS2 cocatalyst confined on graphene sheets-the role of graphene,” J. Phys. Chem. C., vol. 116, pp. 25415-25424, 2012.
[14] A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C. Y. Chim, G. Galli, and F. Wang, “Emerging photoluminescence in monolayer MoS2,” Nano Lett., vol. 10, pp. 1271-1275, 2010.
[15] C. H. Ho, “Optical study of the structural change in ReS2 single crystals using polarized thermoreflectance spectroscopy,” Opt. Express., vol. 13, pp. 8-19, 2005.
[16] H. J. Lamfers, A. Meetsma, G. A. Wiegers, and J. L. de Boer, “The crystal structure of some rhenium and technetium dichalcogenides,” J. Alloys Compd., vol. 241, pp. 34-39, 1996.
[17] M. Hafeez, L. Gan, H. Li, Y. Ma, and T. Zhai, “Large-area bilayer ReS2 film/multilayer ReS2 flakes synthesized by chemical vapor deposition for high performance photodetectors,” Adv. Funct. Mater., vol. 26, pp. 4551–4560, 2016.
[18] B. Jariwala, D. Voiry, A. Jindal, B. A. Chalke, R. Bapat, A. Thamizhavel, M. Chhowalla, M. Deshmukh, and A. Bhattacharya, “Synthesis and characterization of ReS2 and ReSe2 layered chalcogenide single crystals,” Chem. Mater., vol. 28, pp. 3352-3359, 2016.
[19] S. Yang, S. Tongay, Q. Yue, Y. Li, B. Li, and F. Lu, "High-performance few-layer Mo-doped ReSe2 nanosheet photodetectors," Sci. Rep., vol. 4, pp. 5442, 2014.
[20] B. L. Wheeler, J. K. Leland, and A. J. Bard, “Semiconductor electrodes LX. photoelectrochemistry of p-rhenium disulfide and p-rhenium diselenide in aqueous solutions,” J. Electrochem. Soc., vol. 133, issue. 2, pp. 358-361, 1986.
[21] F. Qi, X. Wang, B. Zheng, Y. Chen, B. Yu, J. Zhou, J. He, P. Li, W. Zhang, and Y. Li, "Self-assembled chrysanthemum-like microspheres constructed by few-layer ReSe2 nanosheets as a highly efficient and stable electrocatalyst for hydrogen evolution reaction," Electrochim. Acta, vol. 224, pp. 593-599, 2017.
[22] C. H. Ho, Y. S. Huang, P. C. Liao, and K. K. Tiong, "Crystal structure and band-edge transitions of ReS2−xSex layered compounds," J. Phys. Chem. Solids, vol. 60, pp. 1797-1804, 1999.
[23] J. V. Marzik, R. Kershaw, K. Dwight, and A. Wold, "Photoelectronic properties of ReS2 and ReSe2 single crystals," J. Solid State Chem., vol. 51, pp. 170-175, 1984.
[24] E. Liu, M. Long, J. Zeng, W. Luo, Y. Wang, Y. Pan, W. Zhou, B. Wang, W. Hu, Z. Ni, Y. You, X. Zhang, S. Qin, Y. Shi, K. Watanabe, T. Taniguchi, H. Yuan, H. Y. Hwang, Y. Cui, F. Miao, and D. Xing, "High responsivity phototransistors based on few‐layer ReS2 for weak signal detection," Adv. Funct. Mater., vol. 26, pp. 1938-1944, 2016.
[25] S. H. Jo, H. Y. Park, D. H. Kang, J. Shim, J. Jeon, S. Choi, M. Kim, Y. Park, J. Lee, Y. J. Song, S. Lee, and J. H. Park, "Broad detection range rhenium diselenide photodetector enhanced by (3‐aminopropyl) triethoxysilane and triphenylphosphine treatment," Adv. Mater., vol. 28, pp. 6711-6718, 2016.
[26] A. J. Waldau, M. C. L. Steiner, G. J. Waldau, and E. Bucher, “WS2 thin films prepared by sulphurization,” Appl. Surf. Sci., vol. 70-71, pp. 731-736, 1993.
[27] Q. H. Wang, K. K. Zadeh, A. Kis, J. N. Coleman, and M. S. Strano, “Electronics and optoelectronics of two-dimensional transition metal dichalcogenides,” Nature Nanotech., vol. 7, pp. 699-712, 2012.
[28] A. K. Rai, R. S. Bhattacharya, J. S. Zabinski, and K. Miyoshi, “A comparison of the wear life of as-deposited and ion-irradiated WS2 coatings,” Surf. Coat. Technol., vol. 92, pp. 120-128, 1997.
[29] R. Vaidya, M. Dave, S. S. Patel, S. G. Patel, and A. R. Jani, “Growth of molybdenum disulphide using iodine as transport material,” Pramana., vol. 63, pp. 611-616, 2004.
[30] M. Binnewies, R. Glaum, M. Schmidt, and P. Schmidt, “Chemical vapor transport reactions - a historical review,” Z. Anorg. Allg. Chem., vol. 639, pp. 219-229, 2013.
[31] A. Ubaldini, J. Jacimovic, N. Ubrig, and E. Giannini, “Chloride-driven chemical vapor transport method for crystal growth of transition metal dichalcogenides,” Cryst. Growth Des., vol. 13, pp. 4453-4459, 2013.
[32] M. M. Furchi, D. K. Polyushkin, A. Pospischil, and T. Mueller, “Mechanisms of photoconductivity in atomically thin MoS2,” Nano Lett., vol. 14, pp. 6165-6170, 2014.
[33] W. Zhu, T. Low, Y. H. Lee, H. Wang, D. B. Farmer, J. Kong, F. Xia, and P. Avouris, “Electronic transport and device prospects of monolayer molybdenum disulphide grown by chemical vapour deposition,” Nat. Commun., vol. 5, pp. 3087-1-3087-8, 2014.
[34] R. S. Chen, T. H. Yang, H. Y. Chen, L. C. Chen, K. H. Chen, Y. J. Yang, C. H. Su, and C. R. Lin, “Photoconduction mechanism of oxygen sensitization in InN nanowires,” Nanotechnology, vol. 22, pp. 425702, 2011.
[35] M. Buscema, J. O. Island, D. J. Groenendijk, S. I. Blanter, G. A. Steele, H. S. J. van der Zant, and A. C. Gomez, “Photocurrent generation with two-dimensional van der Waals semiconductors,” Chem. Soc. Rev., vol. 44, pp. 3691-3718, 2015.
[36] M. M. Furchi, D. K. Polyushkin, A. Pospischil, and T. Mueller, “Mechanisms of photoconductivity in atomically thin MoS2,” Nano Lett., vol. 14, pp. 6165-6170, 2014.
[37] J. Dong and D. A. Drabold, "Atomistic structure of band-tail states in amorphous silicon," Phys. Rev. Lett., vol. 80, pp. 1928-1931, 1998.
[38] W. Choi, N. Choudhary, G. H. Han, J. Park, D. Akinwande, and Y. H. Lee, "Recent development of two-dimensional transition metal dichalcogenides and their applications," Mater. Today, vol. 20, pp. 116-130, 2017.
[39] J. Shim, A. Oh, D. H. Kang, S. Oh, S. K. Jang, J. Jeon, M. H. Jeon, M. Kim, C. Choi, J. Lee, S. Lee, G. Y. Yeom, Y. J. Song, and J. H. Park, "High‐performance 2D rhenium disulfide (ReS2) transistors and photodetectors by oxygen plasma treatment," Adv. Mater., vol. 28, pp. 6985-6992, 2016.
[40] Y. Feng, W. Zhou, Y. Wang, J. Zhou, E. Liu, Y. Fu, Z. Ni, X. Wu, H. Yuan, F. Miao, B. Wang, X. Wan, and D. Xing, "Raman vibrational spectra of bulk to monolayer ReS2 with lower symmetry," Phys. Rev. B, vol. 92, pp. 054110, 2015.
[41] D. A. Chenet, O. B. Aslan, P. Y. Huang, C. Fan, A. M. van der Zande, T. F. Heinz, and J. C. Hone, "In-plane anisotropy in mono- and few-layer ReS2 probed by Raman spectroscopy and scanning transmission electron microscopy," Nano Lett., vol. 15, pp. 5667-5672, 2015.
[42] F. Liu, S. Zheng, A. Chaturvedi, V. Zólyomi, J. Zhou, Q. Fu, C. Zhu, P. Yu, Q. Zeng, N. D. Drummond, H. J. Fan, C. Kloc, V. I. Fal'ko, X. He, and Z. Liu, "Optoelectronic properties of atomically thin ReSSe with weak interlayer coupling," Nanoscale, vol. 8, pp. 5826-5834, 2016.
[43] W. Wen, Y. Zhu, X. Liu, H. P. Hsu, Z. Fei, Y. Chen, X. Wang, M. Zhang, K. H. Lin, F. S. Huang, Y. P. Wang, Y. S. Huang, C. H. Ho, P. H. Tan, C. Jin, and L. Xie, "Anisotropic spectroscopy and electrical properties of 2D ReS2(1–x)Se2x alloys with distorted 1T structure," Small, vol. 13, p. 1603788, 2017.
[44] I. Balberg and R. Naidis, "Sensitization of the minority-carrier lifetime in a photoconductor," Phys. Rev. B, vol. 57, pp. R6783-R6786, 1998.
[45] Y. Cao, K. Cai, P. Hu, L. Zhao, T. Yan, W. Luo, X. Zhang, X. Wu, K. Wang, and H. Zheng, "Strong enhancement of photoresponsivity with shrinking the electrodes spacing in few layer GaSe photodetectors," Sci. Rep., vol. 5, pp. 8130, 2015.
[46] H. Liu, B. Xu, J. M. Liu, J. Yin, F. Miao, C. G. Duanc, and X. G. Wana, “Highly efficient and ultrastable visible-light photocatalytic water splitting over ReS2,” Phys. Chem. Chem. Phys., vol. 18, pp. 14222-14227, 2016.