本實驗利用溶液法製備氧化鋅錫薄膜電晶體(ZTO TFT)，作為半導體元件的主動層，ZTO TFT 具備良好的轉換特性曲線、載子遷移率及開關電流比等特性。ZTO 本身是一種氧化物薄膜，在製備的過程中無法避免氧空缺的產生，氧空缺受到一定能量的光源照射時，會被激發成帶正電氧空缺並產生額外的光電子。因此本實驗將ZTO TFT 作為一個基本的感光電晶體，透過以不同波長(405nm、520nm及635nm)及功率密度的雷射光去照射ZTO 並計算其光響應度、光敏感度及動態光響應以判定ZTO TFT 做為一個光感測電晶體的優劣。本實驗所製作的ZTOTFT 是將ZTO 前驅液使用旋轉塗佈的方式塗佈10 層，因此以下會以10-ZTOTFT 來作簡稱，而10-ZTO TFT 分別在不照光時，及以405nm、520nm 及635nm的雷射光0.5mW/cm2 的功率密度照射，量測其ID-VG 特性曲線，可以得出最大光響應的值依序為16.35、2.31、~0 A/W。
由於 ZTO 的中性氧空缺分布於能隙的下半部，故相較於520nm 及635nm 的雷射光，405nm 的雷射光可激發較多數量的中性氧空缺，獲得較高的光響應度。為了改善ZTO TFT 在520nm 及635nm 雷射光照射下的光響應度較小的缺點，本實驗透過濺鍍法添加金奈米粒子(Au NPs)於10-ZTO 薄膜上方，作為一個新的光感測電晶體(Au NPs decorated ZTO TFT)，期望藉由金奈米粒子表面電漿共振效應，吸收特定波長之可見光，並轉換成光電流。Au NPs decorated 10-ZTO TFT 在405nm、520nm 及635nm 的雷測光以0.5mW/cm2 的功率密度照射下，量測ID-VG特性曲線所計算出光響應度分別為35.13、13.02、6.25A/W，確定添加金奈米粒子可使10-ZTO TFT 在405nm、520nm 及635nm 的雷射光照射下皆可以增幅光響應度。
為了確立光感測器的性質，因此我們會透過調控不同的光源波長、功率密度及閘極偏壓來對10-ZTO TFT 及Au NPs decorated 10-ZTO TFT 進行一系列的開關光源的 ID-t(汲極電流對時間之變化)電性量測。在持續照光200s 時，相較於10-ZTO TFT，Au NPs decorated 10-ZTO TFT 在施加正閘極偏壓時可放大光電流，在施加負閘極偏壓時會抑制光電流，此效應在長波長、低功率密度照射時更為顯著，可達到主動式的控制光反應電流，以製成在可見光波段可主動式開關的光感測器。而進行重複開關實驗(開光1s-關光10s，重複40 次)時，無論是否添加金奈米粒子，在負閘極偏壓下，各種光源條件皆無法達到快速開關的目的，而在正閘極偏壓下，因為TFT 部分的電子被ZTO 層及SiO2 層之間的缺陷捕捉而導致電流值不斷下降，而此電流下降的情形在開關光源的操作下可以使光電流複合速度增加，達到更加快速的開關性質。但在正閘極偏壓下，添加金奈米粒子具有增加光電流效應，故其開關速度會較10-ZTO TFT 為緩慢。
最後透過繪製 10-ZTO 及金奈米粒子接觸後的能帶結構圖，以及施加閘極偏壓後能帶圖彎曲的情形，以解釋在進行不同條件操作下，添加金奈米粒子如何影響10-ZTO TFT 產生不同的光電流增幅的結果。

In this study, zinc tin oxide thin film transistor (ZTO TFT) was prepared by solution method and prepared by spin-coating 10 layers of ZTO precursor solution, so it is referred 10-ZTO TFT. By measure ID-VG characteristic curves of 10-ZTO TFT in dark, and under light illumination with 0.5mW/cm2 power density, the maximum responsivities are 16.35, 2.31, ~0 A/W for the light of wavelength 405nm, 520nm and 635nm, respectively. In order to improve the weak responsivity of ZTO TFT under 520nm and 635nm light illumination, gold nanoparticles (Au NPs) are added on the 10-ZTO thin film by sputtering, as a new light-sensing transistors (Au NPs decorated ZTO TFT). Under the illumination of 405nm, 520nm and 635nm laser with 0.5mW/cm2 power density, Au NPs decorated 10-ZTO TFT shows the responsivities of 35.13, 13.02, 6.25A/W.
Compared with the 10-ZTO TFT, the Au NPs decorated 10-ZTO TFT can amplify photocurrent under positive gate bias, and suppress photocurrent under negative gate bias during 200s illumination. For the repeating light on-off cyclic test, regardless of whether or not adding gold nanoparticles, fast switching response is not attainable under the negative gate bias. Nevertheless, under the positive gate bias, electrons in the TFT channel are captured by the defects between ZTO and SiO2 dielectrics, which increase the photocurrent recombination rate under the operation of the repeating switching experiment.
Finally, by plotting the energy band diagram of 10-ZTO and gold nanoparticle in contact, and the band bending after applying the gate bias, the effects of adding gold nanoparticles on the photo-responses of 10-ZTO TFT under different operating conditions are discussed.

[1] Tanaka, I.; Oba, F.; Tatsumi, K.; Kunisu, M.; Nakano, M.; Adachi, H. Theoretical Formation Energy of Oxygen-Vacancies in Oxides. Materials Transactions. 2002, 43, 1426-1429. DOI：10.2320/matertrans.43.1426.
[2] Jang, J. T.; Park, J.; Ahn, B. D.; Kim, D. M.; Choi, S. J.; Kim, H. S.; Kim, D. H. Study on the Photoresponse of Amorphous In-Ga-Zn-O and Zinc Oxynitride Semiconductor Devices by the Extraction of Sub-Gap-State Distribution and Device Simulation. ACS Applied Materials & Interfaces. 2015, 7, 15570-15577. DOI: 10.1021/acsami.5b04152.
[3] Peiris, S.; McMurtrie J.; Zhu, H. Y. Metal nanoparticle photocatalysts: emerging processes for green organic synthesis. Catalysis Science & Technology. 2016, 6, 320-338. DOI: 10.1039/c5cy02048d.
[4] El-Brolossy, T.A.; Abdallah, T.; Mohamed, M.B.; Abdallah, S.; Easawi, K.; Negm, S. Talaat, H. Shape and size dependence of the surface plasmon resonance of gold nanoparticles studied by Photoacoustic technique. The European Physical Journal Special Topics. 2008, 153, 361-364. DOI: 10.1140/epjst/e2008-00462-0.
[5] Liu, Y.; Cheng, R.; Liao, L.; Zhou, H.; Bai, J.; Liu, G.; Liu, L.; Huang, Y.; Duan, X. Plasmon resonance enhanced multicolour photodetection by graphene. Nature Communications. 2011, 2, 579. DOI: 10.1038/ncomms1589.
[6] Zhang, L.; Ding, N.; Lou, L.; Iwasaki, K.; Wu, H.; Luo, Y.; Li, D.; Nakata, K.; Fujishima, A.; Meng, Q. Localized Surface Plasmon Resonance Enhanced Photocatalytic Hydrogen Evolution via Pt@Au NRs/C3N4 Nanotubes under Visible-Light Irradiation. Advanced Functional Materials. 2019, 29, 1806774. DOI: 10.1002/adfm.201806774
[7] Clavero, C. Plasmon-induced hot-electron generation at nanoparticle/metaloxide interfaces for photovoltaic and photocatalytic devices. Nature Photonics. 2014, 8, 95-103. DOI: 10.1038/NPHOTON.2013.238.
[8] Cresi, J. S. P.; Spadaro, M. C.; D’Addato, S.; Valeri, S.; Benedetti, S.; Catone, A. D. B. D.; Mario, L. D.; O’Keeffe, P.; Paladini, A.; Bertoni, G.; Luches, P. Highly efficient plasmon-mediated electron injection into cerium oxide from embedded silver nanoparticles. Nanoscale. 2019, 11, 10282-10291. DOI: 10.1039/c9nr01390c.
[9] Kojori, H. S.; Yun, J. H.; Paik, Y.; Kim, J.; Anderson, W. A.; Kim, S. J. Plasmon Field Effect Transistor for Plasmon to Electric Conversion and Amplification. Nano Letters. 2016, 16, 250-254. DOI: 10.1021/acs.nanolett.5b03625.
[10] Oba, F.; Togo, A.; Tanaka, I.; Paier, J.; Kresse, G. Defect energetics in ZnO: A hybrid Hartree-Fock density functional study. PHYSICAL REVIEW B. 2008, 77, 245202. DOI: 10.1103/PhysRevB.77.245202.
[11] Liu, P. T.; Chou, Y. T.; Teng, L. F. Charge pumping method for photosensor application by using amorphous indium-zinc oxide thin film transistors. APPLIED PHYSICS LETTERS. 2009, 94, 242101. DOI: 10.1063/1.3155507.
[12] Lany, S.; Zunger, A. Anion vacancies as a source of persistent photoconductivity in II-VI and chalcopyrite semiconductors. PHYSICAL REVIEW B. 2005, 72, 035215. DOI: 10.1103/PhysRevB.72.035215.
[13] Thomas, S. R.; Pattanasattayavong, P.; Anthopoulos, T. D. Solutionprocessable metal oxide semiconductors for thin-film transistor applications. Chem. Soc. Rev. 2013, 42, 6910-6923. DOI: 10.1039/c3cs35402d.
[14] Choi, J. Y.; Lee, S. Y. Comprehensive Review on the Development of High Mobility in Oxide Thin Film Transistors. Journal of the Korean Physical Society, 2017, 71, 0-0. DOI: 10.3938/jkps.71.0.
[15] Fortunato, E.; Barquinha, P.; Martins R. Oxide Semiconductor Thin-Film Transistors: A Review of Recent Advances. Adv. Mater. 2012, 24, 2945– 2986. DOI: 10.1002/adma.201103228. DOI: 10.1002/adma.201103228.
[16] Yu, H.; Peng, Y.; Yang, Y.; Li, Z. Y. Plasmon-enhanced light–matter interactions and applications. npj Computational Materials, 2019, 5, 45. DOI：
10.1038/s41524-019-0184-1.
[17] Zhang, N.; Han, C.; Fu, X.; Xu, Y. J. Function-Oriented Engineering of Metal-Based Nanohybrids for Photoredox Catalysis: Exerting Plasmonic Effect and Beyond. Chem. 2018, 4, 1832–1861. DOI ： 10.1016/j.chempr.2018.05.005.
[18] Hamza, A.; Khames, A.; Lesewed, A.; Saad, M. Design an Optical Transducer for Pressure Measurement. International Research Journal of Engineering and Technology, 2016, 3, 1037-1041.
[19] Sood, A. K.; Zeller, J. W.; Puri, Y. R.; Rouse, C.; Haldar, P.; Efstathiadis, H.; Dhar, N.K.; Wijewarnasuriya, P. S. SiGe Focal Plane Array Detector Technology for Near-Infrared Imaging. International Journal of Engineering Research and Technology, 2017, 10, 81-103.
[20] Shive, J .N. The Properties of Germanium Phototransistors, JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. 1953, 43, 239-244. DOI：10.1364/JOSA.43.000239.
[21] Yu, J.; Shin, S. W.; Lee, K. H.; Park, J. S.; Kang, S. J. Visible-light phototransistors based on InGaZnO and silver nanoparticles. J. Vac. Sci. Technol. B, 2015, 33, 061211. DOI：10.1116/1.4936113.
[22] Hwang, J. D.; Wang, F. H.; Kung, C. Y.; Chan, M. C. Using the Surface Plasmon Resonance of Au Nanoparticles to Enhance Ultraviolet Response of ZnO Nanorods-Based Schottky-Barrier Photodetectors. IEEE TRANSACTIONS ON NANOTECHNOLOGY, 2015, 14, 318-321. DOI: 10.1109/TNANO.2015.2393877.
[23] Hosseinia, Z. S.; Bafranib, H. A.; Naserib, A.; Moshfegha, A. Z. Highperformance UV‐Vis-NIR photodetectors based on plasmonic effect in Au nanoparticles/ZnO nanofibers. Applied Surface Science, 2019, 483, 1110–1117. DOI：10.1016/j.apsusc.2019.03.284.
[24] Tang, R. F.; Li, G. Q.; Li, C.; Li, J. C.; Zhang, Y. F.; Huang, K.; Ye, J. D.; Li, C.; Kang, J. Y.; Zhang, R.; Zhen, Y. D. Localized surface plasmon enhanced Ga2O3 solar blind photodetectors. Optics Express, 2020, 28, 5731-5740. DOI：10.1364/OE.380017.
[25] Jing, W. K.; Ding, N.; Li, L. Y.; Jiang, F.; Xiong, X.; Liu, N. S.; Zhai, T. Y.; Gao, Y. H. Ag nanoparticles modified large area monolayer MoS2 phototransistors with high responsivity. Optics Express, 2017, 25, 14565-14574. DOI：10.1364/OE.25.014565.
[26] Cresi, J. S. P.; Spadaro, M. C.; Addato, S. D.; Valeri, S.; Benedetti, S.; Bona, A. D.; Catone, D.; Mario, L. D.; Keeffe, P. O.; Paladini, A.; Bertoni G.; Luches, P. Highly efficient plasmon-mediated electron injection into cerium oxide from embedded silver nanoparticles. Nanoscale, 2019, 11, 10282–10291. DOI: 10.1039/c9nr01390c.
[27] Liu, L. C.(2015) Transistors characteristic and electrical stability of zinc tin oxide thin film transistors by solution process. Unpublished doctoral dissertation, National Cheng Kung University, Tainan, Taiwan.
[28] Zhang, Y.; Pluchery, O.; Caillard, L.; Lamic-Humblot, A.; Casale, S.; Chabal, Y. J.; Salmeron M. Sensing the Charge State of Single Gold Nanoparticles via Work Function Measurements. Nano Lett., 2015, 15, 51−55. DOI：10.1021/nl503782s.