本論文研究的奈米材料為二維的GaSe奈米帶。第一部分，為GaSe奈米帶的製備，首先，以原子百分比Ga:Se=55:45配置Ga金屬錠及Se粉末總共5 g接著放入40 cm的石英管內，於抽氣真空的狀態下預留22 cm的生長區域進行封管。接著將其放入爐管進行加熱至980 °C持溫1小時，使其能夠均勻鎔融及混合，取出後進行快速焠火，便可在管壁上得到許多二維的GaSe奈米帶。利用掃描式電匙顯微鏡(Scanning Electron Microscope, SEM)及能量色散X射線光譜儀(Energy-Dispersive X-ray Spectroscopy, EDS)來確認GaSe 奈米帶的組份和GaSe奈米帶的表面型態、厚度、長度。接著使用Raman來確認材料中的特徵振動峰，光致發光 (Photoluminescence)確認GaSe奈米帶的放光範圍。最後透過穿透式顯微鏡 (Transmission Electron Microscope, TEM)來確認材料之成長方向以及材料之缺陷情況。
第二部分，為一系列的GaSe奈米光電元件之製備，一開始將GaSe奈米帶用沾取的方式，使其位於SiO2/Si基板正中間的視窗上，並使用旋轉塗佈的方式分別塗佈上兩層光阻，第一層為495 (A8)，第二層為950 (A2)，接下來使用光學顯微鏡來確認並記錄GaSe奈米帶之位置。在材料位置上設計六至八個指叉電極，指叉電極長度10 μm，重疊長度6-8 μm，電極寬度為1 μm，通道寬度1.5 μm。將元件拿去進行電子束微影接著顯影，最後使用電子束蒸鍍來鍍電極。這裡選擇鎳當作電極來製備元件。
第三部分為光感性能的探討，使用不同波長的光源來檢測，計算出光響應 (Responsivity)、檢測率 (Detectivity)及外部量子效率 (External quantum efficiency, EQE)的數值。在使用450 nm波長的雷射量測並計算後光響應是6.7 AW-1，檢測率是2.8×1013，EQE為1.8×103 %有極高的外部量子效率。但是由於為了研究載流子復合在GaSe納米帶的情況我們使用405 nm，532 nm跟685 nm進行量測，而量測結果表明，使用405 nm的雷射測量結果是最好的，光響應為11 AW-1，檢測率為2.7×1010，外部量子效率為3.3×103 %。經由計算後，可得知power-law中的α值低於1是因為很高的光電載流子重組，而會有很高光電載流子重組，是因為GaSe有光致發光的特性。

The nanomaterials studied in this paper are two-dimensional GaSe nanoribbons. The first part is the preparation of the GaSe nanobelt. First, the Ga metal ingot and the Se powder are arranged in an atomic ratio of Ga:Se=55:45 in total of 5 g. Then placed it in a 40 cm quartz tube and reserve a 22 cm growth area under vacuum to seal the tube. Afterward, put it into the furnace and heat it to 980 °C for 1 hour to make it melt and mix evenly. After taking it out and quickly quenching, we can get many two-dimensional GaSe nanobelts on the wall of quartz tube. Scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS) are used to confirm the composition of GaSe nanobelt and the surface shape, thickness, length of GaSe nanobelt structure. Then use Raman spectrum to confirm the characteristic vibration peak in the material, and PL (Photoluminescence) spectrum to confirm the emission range of the GaSe nanobelts. Finally, the transmission electron microscope (TEM) is used to confirm the growth direction of the material and the defects of the material.
The second part is the preparation of a GaSe nanobelts photodetector. In the beginning, the GaSe nanobelts were sprayed into the window in the middle of the SiO2/Si substrate. Coated with two layers of electron sensitive resist by spin coating. The first layer is 495 (A8) and the second layer is 950 (A2). The optical microscope is used to confirm and record the position of the GaSe nanobelt. The six to eight finger electrodes were located on the material position. The length of the finger electrodes is 10 μm, the overlap length is 6-8 μm, electrode width is 1 μm, and channel width is 1.5 μm. It is used e-beam lithography for the device. Finally, It applied e-beam evaporation to coating metal be the electrode. Here, we choose Ni to be electrode. The third part is the discussion of the photoelectric performance. This experiment is using light sources with different wavelengths for detection. After measuring the device with 450 nm wavelength laser and calculating the values of responsivity, detectivity, and external quantum efficiency (EQE), the results is 6.7 AW-1, 2.8×1013, 1.8×103 %, respectively. It has high external quantum efficiency to study the situation of carrier recombination into the GaSe nanobelt by electric measurement. The incident beam is used to measure at 405 nm, 532 nm and 685 nm. The measurement results show that the laser measurement results using 405 nm are the best, with the responsivity is 11 AW-1, the detectivity is 2.7×1010, and an EQE is 3.3×103%. After calculation, it can be known that the low α value in power-law is due to the high photoelectric carrier recombination, and the high photoelectric carrier recombination is due to the photoluminescence characteristics of GaSe.

[1] H. Gleiter, “nanocrystalline materials”, Materials Science, 1989, 33, 223-31.
[2] J. Zhao, H. Liu, Z. Yu, R. Quhe, S. Zhou, Y. Wang, C. C. Liu, H. Zhong, N. Han, J. Lu, Y. Yao, K. Wu, “Rise of silicene: A competitive 2D material”, Prog. Mater. Sci., 83, 24-151.
[3] R. Venugopal, Z. Ren, S. Datta and M.S. Lundstrom,” Simulating quantum transport in nanoscale transistors: real versusmode-space approaches”, J. Appl. Phys., 2002, 7, 3730-3739.
[4] L. Lutkenhaus, K.D. Hrabak, K. McEnnis and P.T. Hammond, “Elastomeric flexible free-standing hydrogen-bonded nanoscale assemblies”, J. Am. Chem. Soc, 2005, 127, 17228-17234.
[5] A. Ambrosetti1, N. Ferri1, R.A. DiStasio , A. Tkatchenko, “Wavelike charge density fluctuations and van der Waals interactions at the nanoscale”, Science, 2016, 351, 1171-1176.
[6] X. Cai, Y. Luo, B. Liu and H. M. Cheng, “Preparation of 2D material dispersions and their applications”, Chem. Soc. Rev., 2018, 47, 6224-6266.
[7] T. A. Ameen, H. Ilatikhameneh, G. Klimeck and R. Rahman, “Few-layer phosphorene: An ideal 2D material for tunnel transistors”, Sci. Re
p., 2016, 28515, 1-7.
[8] G. Schusteritsch, M. Uhrin and C. J. Pickard, “Single-layered Hittorf’s phosphorus: A wide-bandgap high mobility 2D material”, Nano Lett., 2016, 16, 2975-2980.
[9] J. Hu, Z. Guo, P. E. Mcwilliams, J. E. Darges, D. L. Druffel, A. M. Moran, and S. C. Warren, “Band gap engineering in a 2D material for solar-to-chemical energy conversion”, Nano Lett., 2015, 16, 74-79.
[10] B. Mortazavi, M. Makaremi, M. Shahrokhi, M. Raeisi, C. V. Singh, T. Rabczuk and L. F. C. Pereira., “Borophene hydride: a stiff 2D material with high thermal conductivity and attractive optical and electronic properties”, Nanoscale, 2018, 10, 3759-3768.
[11] F. Schwierz, “Graphene transistors”, Nat. Nanotechnol., 2010, 5, 487-496.
[12] A. N. Grigorenko, M. Polini and K. S. Novoselov, “Graphene plasmonics”, Nature Photon., 2012, 6, 749-758.
[13] F. Xia, T. Mueller, Y.M. Lin, A. V. Garcia and P. Avouris, “Ultrafast graphene photodetector”, Nat. Nanotechnol. 2009, 4, 839-843.
[14] A. Gupta, T. Sakthivel, S. Seal, “Recent development in 2D materials beyond graphene”, Prog. Mater. Sci, 2015, 73, 44-126.
[15] W. H. Xie, Y. Q. Xu, B. G. Liu, and D. G. Pettifor, “Half-metallic ferromagnetism and structural stability of zincblende phases of the transition-metal chalcogenides”, Phys. Rev. Lett., 2003, 91, 1-4.
[16] N.A. Vante, H.Tributsch, O.S. Feria, “Kinetics studies of oxygen reduction in acid medium on novel semiconducting transition metal chalcogenides” Electrochim. Acta, 1995, 40, 567-576.
[17] W. Jaegermann, H.Tributsch, “Interfacial properties of semiconducting transition metal chalcogenides”, Prog. Surf. Sci., 1988, 29, 1-167.
[18] R. H. Bube and E. L. Lind, “Photoconductivity of gallium selenide crystals”, Phys. Rev., 1959, 115, 1159-1164.
[19] A. Kuc, T. Cusati, E. Dib, A. F. Oliveira, A. Fortunelli, G. Iannaccone, T. Heine and G. Fiori, “High-performance 2D p-Type transistors based on GaSe layers: An Ab initio study”, Adv. Electron. Mater., 2017, 1600399, 1-5.
[20] V. Capozzi and M. Montagna, “Optical spectroscopy of extrinsic recombinations in gallium selenide”, Phys. Rev. B, 1989, 40, 3182-3191.
[21] E. Mooser and M. Schlüter, “The band-gap excitons in gallium selenide”, Nuovo Cimento Soc. Ital. Fis., B, 1973, 18, 164-208.
[22] X. Li, M. W. Lin, A. A. Puretzky, J. C. Idrobo, C. Ma, M. Chi, M. Yoon, C. M. Rouleau, I. I. Kravchenko, D. B. Geohegan and K. Xiao, “Controlled vapor phase growth of single crystalline, two-dimensional GaSe crystals with high photoresponse”. Sci. Rep., 2014, 4, 1-9.
[23] R. L. Toullec, M. Balkanski, J. M. Besson and A.Kuhn, “Optical absorption edge of a new GaSe polytype”, Phys. Lett. A, 1975, 55, 245-246.
[24] V. Augelli, C. Manfredotti, R. Murri, and L. Vasanelli, “Hall-mobility anisotropy in GaSe”, Phys. Rev. B, 1978, 17, 3221-3226.
[25] W. Kim, C. Li, F. A. Chaves, D Jiménez, R. D. Rodriguez, J. Susoma, M. A. Fenner, H. Lipsanen, J. Riikonen, “Tunable graphene–GaSe dual heterojunction device”, Adv. Mater., 2016, 28, 1845-1852.
[26] P. A. Hu, Z. Z. Wen, L. F. Wang, P. H. Tan and K. Xiao, “Synthesis of few-layer GaSe nanosheets for high performance photodetectors”, ACS Nano, 2012, 6, 5988-5994.
[27] Y.Zhou, Y. Nie, Y. Liu, K. Yan, J. Hong, C. Jin, Y. Zhou, J. Yin, Z. Liu, and H. Peng, “Epitaxy and photoresponse of two-dimensional GaSe crystals on flexible transparent mica sheets”, ACS Nano, 2014, 8, 1485-1490.
[28] Y. Cao1, K. Cai1, P. Hu, L. Zhao, T. Yan, W. Luo1, 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., 2015, 5, 1-7.
[29] L. Tang, Z. Zhao, S. Yuan, T. Yang, B. Zhou, H. Zhou, “Self-catalytic VLS growth one dimensional layered GaSe nanobelts for high performance photodetectors”. J. Phys. Chem. Solids, 2018, 118, 186-191.
[30] X. Zhong, W. Zhou, Y. Zhou, F. Zhou, C. Liu, Y. Yin, Y. Peng and D. Tang, “High-performance photodetectors based on bandgap engineered novel layer GaSe0.5Te0.5 nanoflakes”, RSC Adv., 2016, 6, 60862–60868.
[31] X. Xiong, Q. Zhang, X. Zhou , B. Jin, H. Li and T. Zhai, “One-step synthesis of p-type GaSe nanoribbons and their excellent performance in photodetectors and phototransistors”, J. Mater. Chem. C, 2016, 4, 7817-7823.
[32] A. Abderrahmane, P, G. Jung, N. H. Kim, P. J. Ko, and A. Sandhu, “Gate-tunable optoelectronic properties of a nano-layered GaSe photodetector”, Opt. Mater. Express, 2017, 7, 587-592.
[33] Q. Zhao, R. Frisenda, P. Gant, D. P. Lara, C. Munuera, M. Garcia-Hernandez, Y. Niu, T. Wang, W. Jie, and A. Castellanos-Gomez, “Toward air stability of thin GaSe devices: avoiding environmental and laser-induced degradation by encapsulation”, Adv. Funct. Mater. 2018, 1805304, 1-8.
[34] G. Wang, Y. Zhang, C. You, B. Liu, Y. Yang, H. Li, A. Cui, D. Lium, H. Yan, “Two dimensional materials based photodetectors”, Infrared Phys. Technol., 2018, 88, 149-173.
[35] H. Huang, P. Wang, Y. Gao, X. Wang, T. Lin, J. Wang, L. Liao, J. Sun, X. Meng, Z. Huang, X. Chen and J. Chu, “Highly sensitive phototransistor based on GaSe nanosheets”, Appl. Phys. Lett., 2015, 107, 1-4.
[36] S.R. Alharbia and A.F.Qasraw, “Design of the ZnS/Ge/GaSe pn interfaces as plasmonic, photovoltaic and mic”, Results Phys., 2017, 7, 4427-4433.
[37] X. Li, M. W. Lin, J. Lin, B. Huang, A. A. Puretzky, C. M, K. Wang, W. Zhou, S. T. Pantelides, M. Chi, I. Kravchenko, J. Fowlkes, C. M. Rouleau, D. B. Geohegan, K. Xiao, “Two-dimensional GaSe/MoSe2 misfit bilayer heterojunctions by van der Waals epitaxy”, Sci. Adv., 2016, 1501882, 1-10.
[38] X. Zhou, J. Cheng, Y. Zhou, T. Cao, H. Hong, Z. Liao, S. Wu, H. Peng, K. Liu and D. Yu, “Strong second-harmonic generation in atomic layered GaSe”, J. Am. Chem. Soc. 2015, 137, 7994-7997.
[39] J. Xia, X. Huang, L. Z. Liu, M. Wang, L. Wang, B. Huang, D. D. Zhu, J. J. Li, C. Z. Guc and X. M. Meng, “CVD synthesis of large-area, highly crystalline MoSe2 atomic layers on diverse substrates and application to photodetectors” Nanoscale, 2014, 6, 8949-8955.
[40] S. Lei, L. Ge, Z. Liu, S. Najmaei, G. Shi, G. You, J. Lou, R. Vajtai and P. M. Ajayan, “Synthesis and photoresponse of large GaSe atomic layers”, Nano Lett., 2013, 13, 2777-2781.
[41] X. Li, L. Basile, B. Huang, C. Ma, J. Lee, I. V. Vlassiouk, A. A. Puretzky, M. W. Lin, M. Yoon, M. Chi, J. C. Idrobo, C. M. Rouleau, B. G. Sumpter, D. B. Geohegan and K. Xiao, “Van der Waals epitaxial growth of two-dimensional single-crystalline GaSe domains on graphene”, ACS Nano, 2015, 9, 8078-8088.
[42] M. Ohyama and Y. Fujita, “Electrical and optical properties in sputtered GaSe thin films”, Surf. Coat. Technol., 2003, 169, 620-623.
[43] C. Julien, E. Hatzikraniotis, A. Chevy and K. Kambas, “Electrical behavior of lithium intercalated layered In-Se compounds”, Mater. Materials Research Bulletin, 1985, 20, 287-292.
[44] T. Ikari, S. Shigetomi and K. Hashimoto, “Crystal structure and raman spectra of InSe”, Physica Status Solidi, 1982, 111, 477-481.
[45] A.M. Mancini, G. Micocci and A. Rizzo, “New materials for optoelectronic devices: growth and characterization of indium and gallium chalcogenide layer compounds”, Materials Chemistry and Physics, 1983, 9, 29-54.
[46] Z. Chen, J. Biscaras and A. Shukla, “A High performance graphene/few-layer InSe photo-detector”, Nanoscale, 2015, 7, 5981-5986.
[47] L. Mengjiao, C.Y. Lin, S.H. Yang, Y.M. Chang, J.K. Chang, F.S. Yang, C. Zhong, W.B. Jian, C.H. Lien, C.H. Ho, H.J. Liu, R. Huang, W. Li, Y.F. Lin, and J. Chu, “High mobilities in layered InSe transistors with Indium-encapsulation-Induced surface charge doping”, Advanced Materials, 2018, 30, 1803690.
[48] C. Julien, E. Hatzikraniotis, A. Chevy and K. Kambas, “Electrical behavior of lithium intercalated layered In-Se Compounds”, Mater. Materials Research Bulletin, 1985, 20, 287-292.
[49] T. Ikari, S. Shigetomi and K. Hashimoto, “Crystal structure and raman spectra of InSe”, physica status solidi, 1982, 111, 477-481.
[50] A.M. Mancini, G. Micocci and A. Rizzo, “New materials for optoelectronic devices: growth and characterization of Indium and gallium chalcogenide layer compounds”, Materials Chemistry and Physics, 1983, 9, 29-54.
[51] Z. Chen, J. Biscaras and A. Shukla, “A high performance graphene/few-layer InSe photo-detector”, Nanoscale, 2015, 7, 5981-5986.
[52] C. Vieu, F. Carcenac, A. Pepin, Y. Chen, M. Mejias, A. Lebib, L. M. Ferlazzo, L. Couraud, H. Launois, “Electron beam lithography: resolution limits and applications”, Appl. Surf. Sci., 2000, 164, 111-117.
[53] A. Tseng, K. Chen, C. D. Chen and K. J. Ma, “Electron beam lithography in nanoscale fabrication: recent development”, IEEE, 2003, 26, 141-149.
[54] T. H. P. Chang, “Proximity effect in electron‐beam lithography”, J. Vac. Sci. Technol., 1975, 12, 1271-1275.
[55] A. N. Broers, A. C. F. Hoole, J. M. Ryan, “Electron beam lithography—Resolution limits”, Microelectron Eng., 1996, 32, 131-142.
[56] J. Fujita, Y. Ohnishi, Y. Ochiai, and S. Matsui, “Ultrahigh resolution of calixarene negative resist in electron beam lithography”, Appl. Phys. Lett., 1996, 68, 1297-1299.
[57] J. A. Eastman, L. J Thompson, D. J. Marshall, “Synthesis of nanophase materials by electron beam evaporation”, Nanostruct. Mater., 1993, 2, 377-382.
[58] J. W. Bae, J. S. Kim, G. Y. Yeom, “Indium-tin-oxide thin film deposited by a dual ion beam assisted e-beam evaporation system”, Nucl. Instrum. Methods Phys. Res., 2001, 178, 311-314.
[59] R. F. Bunshah, S. Jou, S. Prakash, H. J. Doerr, L. Isaacs, A. Wehrsig, C. Yeretzian, H. Cynn and F. Diederic, “Fullerene formation in sputtering and electron beam evaporation”, J. Phys. Chem., 1992, 96, 6866-6869.
[60] F. S. D. Vicente, E. A. A. Rubo and M. S. Li, “Construction of an evaporation system for film deposition via resistive and electron beam sources”, Rev. Bras. Aplicações de Vácuo, 2004, 23, 11-16.
[61] L. Quan, Y. Song, Y. Lin, G. Zhang, Y. Dai, Y. Wu, K. Jin, H. Ding, N. Pan, Y. Luo and X. Wang, “The Raman enhancement effect on a thin GaSe flake and its thickness dependence”, J. Mater. Chem. C, 2015, 3, 11129-11134.
[62] O. D. P. Zamudio, S. Schwarz, M. Sich, I. A. Akimov, M. Bayer, R. C. Schofield, E. A. Chekhovich, B. J. Robinson, N. D. Kay, O. V. Kolosov, A. I. Dmitriev, G. V. Lashkarev, D. N. Borisenko, N. N. Kolesnikov and A. I. Tartakovski, “Photoluminescence of two-dimensional GaTe and GaSe films”, 2D Mater., 2015, 2, 1-10.
[63] W. I. Jeong, S. Y. Kim, J. J. Kim, J. W. Kang, “Thickness dependence of PL efficiency of organic thin films”, Chem. Phys., 2009, 355, 25-30.
[64] Z. Xu, S. Lin, X. Li, S Zhang, Z. Wu, W. Xu, Y. Lu, S. Xu, “Monolayer MoS2/GaAs heterostructure self-driven photodetector with extremely high detectivity”, Nano Energy, 2016, 23, 89-96.
[65] Z. He, J. Guo, S. Li, Z. Lei, L. Lin, Y. Ke, W. Jie, T. Gong, Y. Lin, T. Cheng, W. Huang and X. Zhang, “GaSe/MoS2 Heterostructure with Ohmic-contact electrodes for fast, broadband photoresponse, and self-driven photodetectors”, Adv. Mater. Interfaces, 2020, 1901848, 1-6.
[66] H. Cai, Y. Gu, Y. C. Lin, Y. Yu, D. B. Geohegan and K. Xiao, “Synthesis and emerging properties of 2D layered III–VI metal chalcogenides”, Appl. Phys. Rev., 2019, 6, 041312.
[67] S. X. Yang , Q. Yue , H. Cai , K. D. Wu , C. B. Jiang and S. Tongay, “Highly efficient gas molecule-tunable few-layer GaSe phototransistors”, J. Mater. Chem. C, 2016, 4, 248-253.