以熱氧化金屬鋅膜法製備氧化鋅奈米線紫外光檢測器，鋅薄膜之溝槽藉由聚焦離子束(focus ion beam, FIB)系統切割，隨後藉由熱氧化法於溝槽間成長氧化鋅奈米線。氧化鋅奈米線的直徑約為70 nm，成長方向為[110]且為單晶結構。由室溫PL量測顯現，氧化鋅奈米線於377 nm具有較強之近能隙發光，且較無缺陷階之發光。變溫PL量測顯現，氧化鋅奈米線之室溫PL發光是由於自由激子的複合，當低溫10 K時，PL光譜由表面激子 (surface exciton, SX)和中性受子束縛激子(neutral acceptors bound excitons) 所主導。以紫外光300 nm照射氧化鋅奈米線光檢測器所得到之Gnormalized 為10^-5 m^2V^-1，而光電流之上升時間以及下降時間分別是0.15 s 以及2.1 s。紫外光和可見光之光響應以及鑑別率分別為1.5×10^5以及30，氧化鋅奈米線具有較好之光檢測特性是由於氧化鋅奈米線為單晶結構，且成長方向為[110]。

ZnO nanowire UV sensors were fabricated by thermal oxidation of metallic zinc strips. A trench was cut through the metallic zinc strip by focused ion beam and subsequent thermal oxidation at 450oC results in the formation of ZnO nanowires across the trench. The diameter of the ZnO nanowire is ~ 70 nm, the growth direction is along the [110] direction and is of single crystalline quality. Room temperature photoluminescence (PL) study shows strong near band edge emission at 377 nm and negligible defect related deep level emission. Variable temperature PL study shows that the room temperature PL emission is due to recombination of free excitons, while at 10 K, the PL is dominated by recombination of surface excitons and exciton bound to neutral acceptors. The ZnO nanowire sensor exhibits a normalized gain of ~ 10^-5 m^2V^-1 under 300 nm illuminations with a riese and decay time of 0.15 and 2.1 seconds, respectively. The responsitivity and UV/Visible rejection ratio are 1.5105 A/W and 30, respectively. This extradoinary high photosensing property is due to the high crystalline quality of ZnO [110] nanowires.

[1] J. F. Yan, Y. M. Lu, Y. C. Liu, H.W. Liang, B.H. Li, D.Z. Shen, J.Y. Zhang and X. W. Fan, “Improvement of the crystalline quality of the ZnO epitaxial layer on a low-temperature grown ZnO buffer layer,” J. Cryst. Growth, Vol. 266, pp. 505-510, 2004.
[2] W. Liu, B. Yao, Y. Li, B. Li, C. Zheng, B. Zhang, C. Shan, Z. Zhang, J. Zhang and D. Shen, “Annealing temperature dependent electrical and optical properties of ZnO and MgZnO films in hydrogen ambient,” Appl. Surf. Sci., Vol. 255, pp. 6745-6749, 2009.
[3] C. G. Van de Walle, “Hydrogen as a cause of doping in zinc oxide,” Phys. Rev. Lett., Vol. 85, pp. 1012-1015, 2000.
[4] X. L. Wu, G. G. Siu, C. L. Fu and H. C. Ong, “Photoluminescence and cathodoluminescence studies of stoichiometric and oxygen-deficient ZnO films,” Appl. Phys. Lett., Vol. 78, pp. 2285-2287, 2001.
[5] S. A. Studenikin, N. Golego and M. Cocivera, “Fabrication of green and orange photoluminescent, undoped ZnO films using spray pyrolysis,” J. Appl. Phys., Vol. 84, pp. 2287-2294, 1998.
[6] A. B. Djurišić, Y. H. Leung, K. H. Tam, Y. F. Hsu, L. Ding, W. K. Ge, Y. C. Zhong, K. S. Wong, W. K. Chan, H. L. Tam, K. W. Cheah, W. M. Kwok and D. L. Phillips, “Defect emissions in ZnO nanostructures,” Nanotechnol., Vol. 18, pp. 1-8, 2007.
[7] B. Lin, Z. Fu, Y. Jia and G. Liao, “Defect photoluminescence of undoping ZnO films and its dependence on annealing conditions,” J. Electrochem. Soc., Vol. 148, pp. 110-113, 2001.
[8] G. Roussos, H. J. Schulz and M. Thiede, “Luminescence and related optical properties of iron ions in II–VI compounds,” J. Lumin., Vol. 31-32, pp. 409-411, 1984.
[9] X. T. Zhang, Y. C. Liu, Z. Z. Zhi, J. Y. Zhang, Y. M. Lu, D. Z. Shen, W. Xu, X. W. Fan and X. G. Kong, “Temperature dependence of excitonic luminescence from nanocrystalline ZnO films,” J. Lumin., Vol. 99, pp. 149-154, 2002.
[10] K. Vanheusden, W. L. Warren, C. H. Seager, D. R. Tallant and J. A. Voigt, “Mechanisms behind green photoluminescence in ZnO phosphor powders,” J. Appl. Phys., Vol. 79, pp. 7983-7990, 1996.
[11] Q. Wan, Q. H. Li, Y. J. Chen, T. H. Wang, X. L. He, J. P. Li and C. L. Lin, “Fabrication and ethanol sensing characteristics of ZnO nanowire gas sensors,” Appl. Phys. Lett., Vol. 84, No. 18, pp. 3654-3656, 2004.
[12] N. Cabrera and N. F. Mott, “Theory of the oxidation of metals,” Rep. Prog. Phys., Vol. 12, pp. 163-184, 1949.
[13] S. Rackauskas, A. G. Nasibulin, H. Jiang, Y. Tian, G. Statkute, S. D. Shandakov, H. Lipsanen and E. I. Kauppinen, “Mechanism investigation of ZnO nanowires growth,” Appl. Phys. Lett., Vol. 95, pp. 183114-1 - 183114-3, 2009.
[14] A. M. B. Gonçalves, L. C. Campos, A. S. Ferlauto and R. G. Lacerda, “On the growth and electrical characterization of CuO nanowires by thermal oxidation,” J. Appl. Phys., Vol. 106, pp. 034303-1-034303-5, 2009.
[15] J. B. K. Law, C. B. Boothroyd and J. T. L. Thong, “Site-specific growth of ZnO nanowires from patterned Zn via compatible semiconductor processing,” J. Cryst. Growth., Vol. 310, pp. 2485-2492, 2008.
[16] S. Ren, Y. F. Bai, Jun Chen, S. Z. Deng, N. S. Xu, Q. B. Wu and S. Yang, “Catalyst-free synthesis of ZnO nanowire arrays on zinc substrate by low temperature thermal oxidation,” Mater. Lett., Vol. 61, pp. 666-670, 2007.
[17] T.W. Kim, T. Kawazoe, “Low-temperature orientation-selective growth and ultraviolet emission of single-crystal ZnO nanowires,” Appl. Phys. Lett., Vol. 84, No. 17, pp. 3358-3360, 2004.
[18] H.Haiping, Y.Qian, W.Jingrui, Y.Zhizhen, “Layer-structured ZnO nanowire arrays with dominant surface and acceptor related emissions,” Mater. Lett., Vol. 65, pp. 1351-1354, 2011.
[19] Q. X. Zhao and M. Willander, “Optical recombination of ZnO nanowires grown on sapphire and Si substrates,” Appl. Phys. Lett.,Vol. 83, No. 1, pp. 165-167, 2003.
[20] C. Soci, A. Zhang, B. Xiang, S. A. Dayeh, D. P. R. Aplin, J. Park, X. Y. Bao, Y. H. Lo, and D. Wang, “ ZnO Nanowire UV Photodetectors with High Internal Gain,” Nano Lett., Vol. 7, No. 4, pp. 1003-1009, 2007.
[21] S. Dhara and P. Giri, “ Enhanced UV photosensitivity from rapid thermal annealed vertically aligned ZnO nanowires,” Nanoscale Res. Lett., Vol. 6, pp. 504-1-504-8, 2011.
[22] W. Y. Weng, S. J. Chang, C. L. Hsu, T. J. Hsueh, and S. P. Chang, “A Lateral ZnO Nanowire Photodetector Prepared on Glass Substrate,” J. Electrochem. Soc., Vol. 157, pp. K30-K33, 2010.
[23] Sanjeev Kumar1, Vinay Gupta and K Sreenivas, “Synthesis of photoconducting ZnO nano-needles using an unbalanced magnetron sputtered ZnO/Zn/ZnO multilayer structure,” nanotechnolo., Vol. 16, pp. 1167-1171, 2005.
[24] D. K. Schroder, “Semiconductor Material and Devic Characterization,” 2nd edition, J. Wiley and Sons, New York, 1998.
[25] J. D. Prades, R. J. Diaz, F. H. Ramirez, L. F. Romero, T. Andreu, A. Cirera and A. R. Rodriguez, A. Cornet, J. R. Morante, S. Barth and S. Mathur, “Toward a Systematic Understanding of Photodetectors Based on Individual Metal Oxide Nanowires,” J. Phys. Chem. C, Vol. 112, pp. 14639-14644, 2008.
[26] B. Kumar, H. Gong, S. Vicknesh, S. J. Chua and S. Tripathy, “Luminescence properties of ZnO layers grown on Si-on-insulator substrates,” Appl. Phys. Lett., Vol. 89, pp. 141901-1-141901-3 , 2006.