本實驗探討單根氧化鋅單跟微米柱與銀作金-半-金結構紫外光檢測器其特性與載子傳輸情形的探討，氧化鋅微米柱與銀電極產生一個二維的蕭特基位障，在二維蕭特基位障的影響下，當此元件被強度47.5mW/cm2的UV光激發，相較於一般歐姆接觸的光檢測器它會有較高的光增益值5.325 並且對光的反應也更靈敏。除此之外我們以能帶圖去探討其中載子的傳輸情形，不對稱的I-V特性曲線圖顯示在氧化經晶體兩邊與銀接觸產生的蕭特基位障高度不同，在受光激發下蕭特基位障會因為電洞與表面氧離子子複合而降低，穿隧電流會以指數性提高，並且越高的位障降低得越多，這使得受光激發下的I-V特性曲線圖會越變越對稱，因此可藉由光來控制此元件的電特性；當關閉光源時，氧分子重新吸附在氧化鋅晶體表面上，蕭特基位障高度因此上升，所以穿隧電流會以指數型式遞減，此光檢測器對於光有高靈敏的反應。

In this article, we fabricated a single ZnO microrod M-S-M structure photodetector with Ag Schottky contact. We demonstrate this phonemona by physical band model. ZnO microrod ultraviolet (UV) photodetector with two-dimensional Schottky barrier, which presented a high photocurrent gain of 5.325 under UV illumination with power density 47.5mW/cm. The asymmetric I-V curve was caused by different Schottky barrier at the interface of electrode and ZnO microrod. Under UV light, The I-V curve become more symmetric, the higher the barrier height, the higher the decrease in barrier height. We can control the I-V characteristics of the Zno microrod M-S-M structure by UV light illumination. The reduction of schottky high will also make tunneling current increase exponentially so the pohotreponse of the device in schottky contact is more sensitive than Ohmic contact and high photocurrent gain.

[1] C. Soci, A. Zhang, B. Xiang, S. A. Dayeh, D. P. R. Aplin, J. Park, et al., "ZnO Nanowire UV Photodetectors with High Internal Gain," Nano Letters, vol. 7, pp. 1003-1009, 2007.
[2] K. Liu, M. Sakurai, M. Liao, and M. Aono, "Giant Improvement of the Performance of ZnO Nanowire Photodetectors by Au Nanoparticles," The Journal of Physical Chemistry C, vol. 114, pp. 19835-19839, 2010.
[3] C. Yi-Kuei and H. Franklin Chau-Nan, "The fabrication of ZnO nanowire field-effect transistors combining dielectrophoresis and hot-pressing," Nanotechnology, vol. 20, p. 235202, 2009.
[4] D. Lin, H. Wu, W. Zhang, H. Li, and W. Pan, "Enhanced UV photoresponse from heterostructured Ag–ZnO nanowires," Applied Physics Letters, vol. 94, p. 172103, 2009.
[5] A. Bera and D. Basak, "Role of defects in the anomalous photoconductivity in ZnO nanowires," Applied Physics Letters, vol. 94, p. 163119, 2009.
[6] H. Kind, H. Yan, B. Messer, M. Law, and P. Yang, "Nanowire Ultraviolet Photodetectors and Optical Switches," Advanced Materials, vol. 14, pp. 158-160, 2002.
[7] J. Dai, C. Xu, X. Xu, J. Guo, J. Li, G. Zhu, et al., "Single ZnO Microrod Ultraviolet Photodetector with High Photocurrent Gain," ACS Applied Materials & Interfaces, vol. 5, pp. 9344-9348, 2013.
[8] Z. Y. Zhang, C. H. Jin, X. L. Liang, Q. Chen, and L.-M. Peng, "Current-voltage characteristics and parameter retrieval of semiconducting nanowires," Applied Physics Letters, vol. 88, p. 073102, 2006.
[9] H. M. Manohara, E. W. Wong, E. Schlecht, B. D. Hunt, and P. H. Siegel, "Carbon Nanotube Schottky Diodes Using Ti−Schottky and Pt−Ohmic Contacts for High Frequency Applications," Nano Letters, vol. 5, pp. 1469-1474, 2005.
[10] T.-Y. Wei, P.-H. Yeh, S.-Y. Lu, and Z. L. Wang, "Gigantic Enhancement in Sensitivity Using Schottky Contacted Nanowire Nanosensor," Journal of the American Chemical Society, vol. 131, pp. 17690-17695, 2009.
[11] Y. Hu, J. Zhou, P.-H. Yeh, Z. Li, T.-Y. Wei, and Z. L. Wang, "Supersensitive, Fast-Response Nanowire Sensors by Using Schottky Contacts," Advanced Materials, vol. 22, pp. 3327-3332, 2010.
[12] J. Zhou, Y. Gu, Y. Hu, W. Mai, P.-H. Yeh, G. Bao, et al., "Gigantic enhancement in response and reset time of ZnO UV nanosensor by utilizing Schottky contact and surface functionalization," Applied Physics Letters, vol. 94, p. 191103, 2009.
[13] C. Li, Y. Bando, M. Liao, Y. Koide, and D. Golberg, "Visible-blind deep-ultraviolet Schottky photodetector with a photocurrent gain based on individual Zn2GeO4 nanowire," Applied Physics Letters, vol. 97, p. 161102, 2010.
[14] C. Ke, C. Gang, W. Shujie, L. Linsong, D. Shuxi, Z. Xingtang, et al., "Surface states dominative Au Schottky contact on vertical aligned ZnO nanorod arrays synthesized by low-temperature growth," New Journal of Physics, vol. 9, p. 214, 2007.
[15] G. Cheng, Z. Li, S. Wang, H. Gong, K. Cheng, X. Jiang, et al., "The unsaturated photocurrent controlled by two-dimensional barrier geometry of a single ZnO nanowire Schottky photodiode," Applied Physics Letters, vol. 93, p. 123103, 2008.
[16] G. Cheng, S. Wang, K. Cheng, X. Jiang, L. Wang, L. Li, et al., "The current image of a single CuO nanowire studied by conductive atomic force microscopy," Applied Physics Letters, vol. 92, p. 223116, 2008.
[17] J. Yu, C. X. Shan, X. M. Huang, X. W. Zhang, S. P. Wang, and D. Z. Shen, "ZnO-based ultraviolet avalanche photodetectors," Journal of Physics D: Applied Physics, vol. 46, p. 305105, 2013.
[18] S. Alexandrou, C. C. Wang, T. Y. Hsiang, M. Y. Liu, and S. Y. Chou, "A 75 GHz silicon metal‐semiconductor‐metal Schottky photodiode," Applied Physics Letters, vol. 62, pp. 2507-2509, 1993.
[19] M. Gökkavas, S. Butun, H. Yu, T. Tut, B. Butun, and E. Ozbay, "Dual-color ultraviolet metal-semiconductor-metal AlGaN photodetectors," Applied Physics Letters, vol. 89, p. 143503, 2006.
[20] Y. Jin, J. Wang, B. Sun, J. C. Blakesley, and N. C. Greenham, "Solution-Processed Ultraviolet Photodetectors Based on Colloidal ZnO Nanoparticles," Nano Letters, vol. 8, pp. 1649-1653, 2008.
[21] L. Polenta, M. Rossi, A. Cavallini, R. Calarco, M. Marso, R. Meijers, et al., "Investigation on Localized States in GaN Nanowires," ACS Nano, vol. 2, pp. 287-292, 2008.
[22] R. Calarco, M. Marso, T. Richter, A. I. Aykanat, R. Meijers, A. v.d. Hart, et al., "Size-dependent Photoconductivity in MBE-Grown GaN−Nanowires," Nano Letters, vol. 5, pp. 981-984, 2005.
[23] M. A. Verges, A. Mifsud, and C. J. Serna, "FORMATION OF ROD-LIKE ZINC-OXIDE MICROCRYSTALS IN HOMOGENEOUS SOLUTIONS," Journal of the Chemical Society-Faraday Transactions, vol. 86, pp. 959-963, 1990.
[24] J. A. Sans, A. Segura, F. J. Manjon, B. Mari, A. Munoz, and M. J. Herrera-Cabrera, "Optical properties of wurtzite and rock-salt ZnO under pressure," Microelectronics Journal, vol. 36, pp. 928-932, 2005.
[25] A. Ashrafi and C. Jagadish, "Review of zincblende ZnO: Stability of metastable ZnO phases," Journal of Applied Physics, vol. 102, 2007.
[26] Ü. Özgür, Y. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, et al., "A comprehensive review of ZnO materials and devices," Journal of Applied Physics, vol. 98, p. 041301, 2005.
[27] V. L. Solozhenko, O. O. Kurakevych, P. S. Sokolov, and A. N. Baranov, "Kinetics of the Wurtzite-to-Rock-Salt Phase Transformation in ZnO at High Pressure," The Journal of Physical Chemistry A, vol. 115, pp. 4354-4358, 2011.
[28] L. Schmidt-Mende and J. L. MacManus-Driscoll, "ZnO – nanostructures, defects, and devices," Materials Today, vol. 10, pp. 40-48, 2007.
[29] F. Oba, S. R. Nishitani, S. Isotani, H. Adachi, and I. Tanaka, "Energetics of native defects in ZnO," Journal of Applied Physics, vol. 90, pp. 824-828, 2001.
[30] J. Han, P. Q. Mantas, and A. M. R. Senos, "Defect chemistry and electrical characteristics of undoped and Mn-doped ZnO," Journal of the European Ceramic Society, vol. 22, pp. 49-59, 2002.
[31] V. Sallet, C. Sartel, C. Vilar, A. Lusson, and P. Galtier, "Opposite crystal polarities observed in spontaneous and vapour-liquid-solid grown ZnO nanowires," Applied Physics Letters, vol. 102, pp. 182103-182103, 2013.
[32] X. D. Wang, C. J. Summers, and Z. L. Wang, "Large-scale hexagonal-patterned growth of aligned ZnO nanorods for nano-optoelectronics and nanosensor arrays," Nano Letters, vol. 4, pp. 423-426, 2004.
[33] Y. Peidong, Y. Haoquan, M. Samuel, R. Russo, J. Johnson, R. Saykally, et al., "Controlled growth of ZnO nanowires and their optical properties," Advanced Functional Materials, vol. 12, pp. 323-331, 2002.
[34] M. Mosca, R. Macaluso, C. Cali, R. Butte, S. Nicolay, E. Feltin, et al., "Optical, structural, and morphological characterisation of epitaxial ZnO films grown by pulsed-laser deposition," Thin Solid Films, vol. 539, pp. 55-59, 2013.
[35] Y. R. Ryu, S. Zhu, D. C. Look, J. M. Wrobel, H. M. Jeong, and H. W. White, "Synthesis of p-type ZnO films," Journal of Crystal Growth, vol. 216, pp. 330-334, 2000.
[36] B. J. Jin, S. Im, and S. Y. Lee, "Violet and UV luminescence emitted from ZnO thin films grown on sapphire by pulsed laser deposition," Thin Solid Films, vol. 366, pp. 107-110, 2000.
[37] Z. Han, J. Li, W. He, S. Li, Z. Li, J. Chu, et al., "A microfluidic device with integrated ZnO nanowires for photodegradation studies of methylene blue under different conditions," Microelectronic Engineering, vol. 111, pp. 199-203, 2013.
[38] B. Liu and H. C. Zeng, "Hydrothermal synthesis of ZnO nanorods in the diameter regime of 50 nm," Journal of the American Chemical Society, vol. 125, pp. 4430-4431, 2003.
[39] W. J. Li, E. W. Shi, W. Z. Zhong, and Z. W. Yin, "Growth mechanism and growth habit of oxide crystals," Journal of Crystal Growth, vol. 203, pp. 186-196, 1999.
[40] L. Qian, L. Xifeng, and Z. Jianhua, "Microstructure, optical and electrical properties of gallium-doped ZnO films prepared by sol-gel method," Journal of Alloys and Compounds, vol. 572, pp. 175-179, 2013.
[41] B. B. Lakshmi and C. R. Martin, "Sol-gel template synthesis of semiconductor nanostructures," Proceedings of the Fourth International Symposium on Quantum Confinement: Nanoscale Materials, Devices, and Systems, pp. 47-58, 1997.
[42] L. Spanhel and M. A. Anderson, "Semiconductor clusters in the sol-gel process - quantized aggregation, gelation, and crystal-growth in concentrated ZnO colloids," Journal of the American Chemical Society, vol. 113, pp. 2826-2833, 1991.
[43] D. A. Neamen, "Semiconductor physics and devices: basic principles," McGraq-Hill, 2003.
[44] H. M. Huang, R. S. Chen, H. Y. Chen, T. W. Liu, C. C. Kuo, C. P. Chen, et al., "Photoconductivity in single AlN nanowires by subband gap excitation," Applied Physics Letters, vol. 96, p. 062104, 2010.
[45] C.-H. Lin, R.-S. Chen, T.-T. Chen, H.-Y. Chen, Y.-F. Chen, K.-H. Chen, et al., "High photocurrent gain in SnO2 nanowires," Applied Physics Letters, vol. 93, p. 112115, 2008.
[46] 林麗娟, "X光繞射原理及其應用," p. 132, 1994.
[47] 呂嘉濠, "單一氧化鋅結構之微腔效應與光磊雷射行為," 2013.
[48] R. S. Chen, T. H. Yang, H. Y. Chen, L. C. Chen, K. H. Chen, Y. J. Yang, et al., "Photoconduction mechanism of oxygen sensitization in InN nanowires," Nanotechnology, vol. 22, p. 425702, 2011.
[49] G. Cheng, X. Wu, B. Liu, B. Li, X. Zhang, and Z. Du, "ZnO nanowire Schottky barrier ultraviolet photodetector with high sensitivity and fast recovery speed," Applied Physics Letters, vol. 99, p. 203105, 2011.
[50] J. Wen, X. Zhang, H. Gao, and M. Wang, "Current–voltage characteristics of the semiconductor nanowires under the metal-semiconductor-metal structure," Journal of Applied Physics, vol. 114, p. 223713, 2013.
[51] Q. Yang, X. Guo, W. Wang, Y. Zhang, S. Xu, D. H. Lien, et al., "Enhancing Sensitivity of a Single ZnO Micro-/Nanowire Photodetector by Piezo-phototronic Effect," ACS Nano, vol. 4, pp. 6285-6291, 2010.
[52] D. Li, X. Sun, H. Song, Z. Li, H. Jiang, Y. Chen, et al., "Effect of asymmetric Schottky barrier on GaN-based metal-semiconductor-metal ultraviolet detector," Applied Physics Letters, vol. 99, p. 261102, 2011.
[53] S. J. Wang, W. J. Lu, G. Cheng, K. Cheng, X. H. Jiang, and Z. L. Du, "Electronic transport property of single-crystalline hexagonal tungsten trioxide nanowires," Applied Physics Letters, vol. 94, p. 263106, 2009.
[54] W. Mönch, "Metal-semiconductor contacts: electronic properties," Surface Science, vol. 299–300, pp. 928-944, 1994.
[55] H. Kim, H. Kim, and D.-W. Kim, "Silver Schottky contacts to a-plane bulk ZnO," Journal of Applied Physics, vol. 108, p. 074574, 2010.
[56] J. Dai, C. Xu, J. Guo, X. Xu, G. Zhu, and Y. Lin, "Brush-like SnO2/ZnO hierarchical nanostructure: Synthesis, characterization and application in UV photoresponse," AIP Advances, vol. 3, p. 062108, 2013.
[57] B. Cheng, J. Xu, Z. Ouyang, C. Xie, X. Su, Y. Xiao, et al., "Individual ZnO nanowires for photodetectors with wide response range from solar-blind ultraviolet to near-infrared modulated by bias voltage and illumination intensity," Optics Express, vol. 21, pp. 29719-29730, 2013.