本論文探討單一氧化鋅微結構之微腔效應與光泵浦雷射產生的行為，分別使用固態反應法(solid-state reaction)以及氣相轉移法(vapor phase transport)成長出不同形貌的氧化鋅微晶，並量測單一微晶的顯微光激發光光譜，實現隨機雷射以及WGM雷射的現象。
首先，我們以固態反應法成長具有高品質的光學特性之海膽狀氧化鋅微晶。光激發光光譜展現了其室溫下顯著的激子紫外發光。此外，觀察單一海膽狀氧化鋅微晶之雷射特性，藉由系統性地分析不同晶體大小以及不同激發強度下的光泵浦雷射發光特性。結果顯示海膽狀微晶之隨機雷射具有高品質因子以及低雷射閥值。原因為海膽狀微晶表面布滿的奈米針尖，可視為簡易的分佈式反射鏡，而使得光侷限增強。
其次，以氣相轉移法成長之單一六角柱氧化鋅微晶體可形成一個完整的耳語迴廊模態(Whispering Gallery Mode,WGM)共振腔，同時氧化鋅也是雷射的增益介質，光子會在晶體柱內進行多次的氧化鋅/空氣介面全反射，因此觀察到WGM雷射具有較高的品質因子以及較低的雷射閥值。此外，我們也分析了邊角形貌對WGM雷射的影響。比起平滑邊角柱，光子能侷限在銳利邊角柱內的時間更長，因此銳利邊角柱能具有更高的品質因子以及增益效率。雷射閥值的部分，氧化鋅六角柱WGM的雷射閥值比上述海膽狀氧化鋅微晶隨機雷射低了一個數量級，且接近於目前最低WGM雷射閥值的文獻紀錄。

We report on the observation of optically pumped random lasing and WGM lasing in two different ZnO microstructures synthesized by solid-state reaction and vapor phase transport. The photoluminescence (PL) properties of individual ZnO optical microcavities are investigated by micro-PL measurement.
First, we prepare urchin-like micron-size ZnO cavities with high optical quality by oxidation of the metallic Zn. The growth mechanism of the urchin-like macrostructure is proposed. PL spectra of the ZnO microstructures display a predominant ultraviolet excitonic emission at room temperature. Lasing properties of the individual ZnO urchin-like microstructures are systematically investigated through power and size dependent photoluminescence measurements. This result shows that a low lasing threshold with high quality factor can be achieved due to the high reflectivity of the optical reflectors formed by the tapered nanowire.
Second, ZnO hexagonal microrods synthesized by vapor phase transport provide a lasing microcavity of whispering gallery modes (WGMs) and laser gain medium. The photon propagates in the inner walls as a result of multiple total internal reflections at the ZnO/air interface. Therefore, WGM laser with low threshold and high Q factor could be obtained. The influence of corner shapes of ZnO hexagonal microrods is also studied. Sharp corners increase the Q factor and the slope efficiency due to extending the photon lifetime in microcavity. The value of lasing threshold in ZnO microrods with the sharp coners is one order of magnitude lower than that of urchin-like mictostructures and comparable to the lowest reported WGM lasing thresholds.

[1] A. L. Schawlow and C. H. Townes, "Infrared and optical masers," Physical Review, vol. 112, p. 1940, 1958.
[2] T. H. Maiman, "Stimulated optical radiation in ruby," Nature, vol. 187, p. 493, 1960.
[3] R. N. Hall, G. E. Fenner, J. D. Kingsley, T. J. Soltys, and R. O. Carlson, "Coherent light emission from GaAs junctions," Physical Review Letters, vol. 9, p. 366, 1962.
[4] N. Holonyak and S. F. Bevacqua, "Coherent (visible) light emission from Ga(As1-xPx) junctions," Applied Physics Letters, vol. 1, p. 82, 1962.
[5] T. M. Quist, R. H. Rediker, R. J. Keyes, W. E. Krag, B. Lax, A. L. Mcwhorter, et al., "Semiconductor maser of GaAs," Applied Physics Letters, vol. 1, p. 91, 1962.
[6] K. J. Vahala, "Optical microcavities," Nature, vol. 424, p. 839, 2003.
[7] B. E. A. Saleh and M. C. Teich, "Lasers," in Fundamentals of Photonics, ed, 2007.
[8] J. C. Johnson, H. Yan, P. Yang, and R. J. Saykally, "Optical cavity effects in ZnO nanowire lasers and waveguides," Journal of Physical Chemistry B, vol. 107, p. 8816, 2003.
[9] J. Keeling and N. G. Berloff, "Exciton–polariton condensation," Contemporary Physics, vol. 52, p. 131, 2011.
[10] R. B. Liu and B. S. Zou, "Lasing behaviour from the condensation of polaronic excitons in a ZnO nanowire," Chinese Physical B, vol. 20, p. 047104, 2011.
[11] M. Zamfirescu, A. Kavokin, B. Gil, G. Malpuech, and M. Kaliteevski, "ZnO as a material mostly adapted for the realization of room-temperature polariton lasers," Physical Review B, vol. 65, p. 161205, 2002.
[12] S. Cho, H. Jeong, D. H. Park, S. H. Jung, H. J. Kim, and K. H. Lee, "The effects of vitamin C on ZnO crystal formation," CrystEngComm, vol. 12, p. 968, 2010.
[13] G. C. Yi, C. Wang, and W. I. Park, "ZnO nanorods: synthesis, characterization and applications," Semiconductor Science and Technology, vol. 20, p. S22, 2005.
[14] A. Matsuda, W. Tan, S. Furukawa, and H. Muto, "Morphology-control of crystallites precipitated from ZnO gel films by applying electric field during hot-water treatment," Materials Science in Semiconductor Processing, vol. 16, p. 1232, 2013.
[15] D. Yu, T. Trad, J. T. McLeskey, V. Craciun, and C. R. Taylor, "ZnO nanowires synthesized by vapor phase transport deposition on transparent oxide substrates," Nanoscale Research Letter, vol. 5, p. 1333, 2010.
[16] S. Chu, G. Wang, W. Zhou, Y. Lin, L. Chernyak, J. Zhao, et al., "Electrically pumped waveguide lasing from ZnO nanowires," Nature Nanotechnology, vol. 6, p. 506, 2011.
[17] J. Dai, C. X. Xu, and X. W. Sun, "ZnO-microrod/p-GaN heterostructured whispering-gallery-mode microlaser diodes," Advanced Materials, vol. 23, p. 4115, 2011.
[18] Y. Li, B. Yao, R. Deng, B. Li, Z. Zhang, C. Shan, et al., "A comparative study on electroluminescence from ZnO-based double heterojunction light emitting diodes grown on different lattice mismatch substrates," Journal of Alloys and Compounds, vol. 575, p. 233, 2013.
[19] F. H. Hsu, N. F. Wang, Y. Z. Tsai, M. C. Chuang, Y. S. Cheng, and M. P. Houng, "Study of working pressure on the optoelectrical properties of Al–Y codoped ZnO thin-film deposited using DC magnetron sputtering for solar cell applications," Applied Surface Science, vol. 280, p. 104, 2013.
[20] C. Gao, X. Li, Y. Wang, L. Chen, X. Pan, Z. Zhang, et al., "Titanium dioxide coated zinc oxide nanostrawberry aggregates for dye-sensitized solar cell and self-powered UV-photodetector," Journal of Power Sources, vol. 239, p. 458, 2013.
[21] C. C. Huang, F. H. Wang, and C. F. Yang, "Effects of deposition temperature and hydrogen flow rate on the properties of the Al-doped ZnO thin films and amorphous silicon thin-film solar cells," Applied Physics A, vol. 112, p. 877, 2013.
[22] W. Jing, L. Niu, B. Wang, L. Chen, and Z. Jiang, "Simulation and ZnO nanowires-based generation of a hierarchical structure on an optical fiber core," Applied Surface Science, vol. 280, p. 186, 2013.
[23] K. J. Lee, H. Oh, M. Jo, K. Lee, and S. S. Yang, "An ultraviolet sensor using spin–coated ZnO nanoparticles based on surface acoustic waves," Microelectronic Engineering, vol. 111, p. 105, 2013.
[24] H. Oh, K. J. Lee, J. Baek, S. S. Yang, and K. Lee, "Development of a high sensitive pH sensor based on shear horizontal surface acoustic wave with ZnO nanoparticles," Microelectronic Engineering, vol. 111, p. 154, 2013.
[25] M. Karimi, J.Saydi, M.Mahmoodi, J.Seidi, M.Ezzati, S.ShamsiAnari, et al., "A comparative study on ethanol gas sensing properties of ZnO and Zn0.94Cd0.06O nanoparticles," Journal of Physics and Chemistry of Solids, vol. 74, p. 1392, 2013.
[26] H. Cao and Y. G. Zhao, "Random laser action in semiconductor powder," Physical Review Letters, vol. 82, p. 2278, 1999.
[27] Y. Tian, X. Ma, L. Jin, and D. Yang, "Electrically pumped ultraviolet random lasing from ZnO films: Compensation between optical gain and light scattering," Applied Physics Letters, vol. 97, p. 251115, 2010.
[28] S. F. Yu, C. Yuen, S. P. Lau, W. I. Park, and G. C. Yi, "Random laser action in ZnO nanorod arrays embedded in ZnO epilayers," Applied Physics Letters, vol. 84, p. 3241, 2004.
[29] Ü. Özgür, Y. I. Alivov, A. T. C. Liu, M. A. Reshchikov, S. Doğan, V. Avrutin, et al., "A comprehensive review of ZnO materials and devices," Journal of Applied Physics, vol. 98, p. 041301, 2005.
[30] M. L. Gorodetsky, A. A. Savchenkov, and V. S. Ilchenko, "Ultimate Q of optical microsphere resonators," Optics Letters, vol. 21, p. 453, 1996.
[31] V. Sandoghdar, F. Treussart, J. Hare, V. L. Seguin, J. M. Raimond, and S. Haroche, "Very low threshold whispering-gallery-mode microsphere laser," Physical Review A, vol. 54, p. R1777, 1996.
[32] J. Wiersig, "Hexagonal dielectric resonators and microcrystal lasers," Physical Review A, vol. 67, p. 023807, 2003.
[33] D. Wang, H. W. Seo, C. C. Tin, M. J. Bozack, J. R. Williams, M. Park, et al., "Lasing in whispering gallery mode in ZnO nanonails," Journal of Applied Physics, vol. 99, p. 093112, 2006.
[34] C. P. Dietrich, M. Lange, T. Bontgen, and M. Grundmann, "The corner effect in hexagonal whispering gallery microresonators," Applied Physics Letters, vol. 101, p. 141116, 2012.
[35] X. Q. Wei, B. Y. Man, M. Liu, C. S. Xue, H. Z. Zhuang, and C. Yang, "Blue luminescent centers and microstructural evaluation by XPS and Raman in ZnO thin films annealed in vacuum, N2 and O2," Physica B, vol. 388, p. 145, 2007.
[36] B. K. Meyer, H. Alves, D. M. Hofmann, W. Kriegseis, D. Forster, F. Bertram, et al., "Bound exciton and donor–acceptor pair recombinations in ZnO," physica status solidi (b), vol. 241, p. 231, 2004.
[37] H. S. Kang, J. S. Kang, J. W. Kim, and S. Y. Lee, "Annealing effect on the property of ultraviolet and green emissions of ZnO thin films," Journal of Applied Physics, vol. 95, p. 1246, 2004.
[38] H. S. Kang, J. S. Kang, S. S. Pang, E. S. Shim, and S. Y. Lee, "Variation of light emitting properties of ZnO thin films depending on post-annealing temperature," Materials Science and Engineering B, vol. 102, p. 313, 2003.
[39] B. Lin, Z. Fu, Y. Jia, and G. Liao, "Defect photoluminescence of undoping ZnO films and its fependence on annealing conditions," Journal of The Electrochemical Society, vol. 183, p. G110, 2001.
[40] K. Vanheusden, C. H. Seager, W. L. Warren, D. R. Tallant, and J. A. Voigt, "Correlation between photoluminescence and oxygen vacancies in ZnO phosphors," Applied Physics Letters, vol. 68, p. 403, 1996.
[41] E. G. Bylander, "Surface effects on the low‐energy cathodoluminescence of zinc oxide," Journal of Applied Physics, vol. 49, p. 1188, 1978.
[42] 謝嘉民, 賴一凡, 林永昌, and 枋志堯, 光激發螢光量測原理、架構及應用, 2005.
[43] D. M. Bagnall, Y. F. Chen, Z. Zhu, T. Yao, S. Koyama, M. Y. Shen, et al., "Optically pumped lasing of ZnO at room temperature," Applied Physics Letters, vol. 70, p. 2230, 1997.
[44] C. H. Ho, Y. H. Liang, and Y. J. Chen, "Band-edge transitions of a metallorganic chemical vapor deposited ZnO film on Si by thermoreflectance spectroscopy," Electrochemical and Solid-State Letters, vol. 9, p. G312, 2006.
[45] F. Liu, P. J. Cao, H. R. Zhang, C. M. Shen, Z. Wang, J. Q. Li, et al., "Well-aligned zinc oxide nanorods and nanowires prepared without catalyst," Journal of Crystal Growth, vol. 274, p. 126, 2005.
[46] A. Umar, S. H. Kim, Y. S. Lee, K. S. Nahm, and Y. B. Hahn, "Catalyst-free large-quantity synthesis of ZnOnanorods by a vapor–solid growth mechanism: Structural and optical properties," Journal of Crystal Growth, vol. 282, p. 131, 2005.
[47] P. Viswanathamurthi, N. Bhattarai, H. Y. Kim, and D. R. Lee, "The photoluminescence properties of zinc oxide nanofibres prepared by electrospinning," Nanotechnology, vol. 15, p. 320, 2004.
[48] 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, p. 182103, 2013.
[49] X. 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, p. 423, 2004.
[50] P. Yang, H. Yan, S. Mao, R. Russo, J. Johnson, R.Saykally, et al., "Controlled growth of ZnO nanowires and their optical properties," Advanced Functional Materials, vol. 12, p. 323, 2002.
[51] M. Mosca, R. Macaluso, C. Calì, R. Butté, 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, p. 55, 2013.
[52] 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, p. 330, 2000.
[53] 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, p. 107, 2000.
[54] 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, p. 199, 2013.
[55] 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, p. 4430, 2003.
[56] 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, p. 186, 1999.
[57] 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, p. 175, 2013.
[58] B. B. Lakshmi, P. K. Dorhout, and C. R. Martin, "Sol-gel template synthesis of semiconductor nanostructures," Chemistry of Materials, vol. 9, p. 857, 1997.
[59] 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, p. 2826, 1991.
[60] H. J. Fan, R. Scholz, F. M. Kolb, and M. Zacharias, "Two-dimensional dendritic ZnO nanowires from oxidation of Zn microcrystals," Applied Physics Letters, vol. 85, p. 4142, 2004.
[61] S. J. Han, T. H. Jang, Y. B. Kim, B. G. Park, J. H. Park, and Y. H. Jeong, "Magnetism in Mn-doped ZnO bulk samples prepared by solid state reaction," Applied Physics Letters, vol. 83, p. 920, 2003.
[62] S. Cho, J. Ma, Y. Kim, Y. Sun, G. K. L. Wong, and J. B. Ketterson, "Photoluminescence and ultraviolet lasing of polycrystalline ZnO thin films prepared by the oxidation of the metallic Zn," Applied Physics Letters, vol. 75, p. 2761, 1999.
[63] S. N. Mohammad, "For nanowire growth, vapor-solid-solid (vapor-solid) mechanism is actually vapor-quasisolid-solid (vapor-quasiliquid-solid) mechanism," The Journal of Chemical Physics, vol. 131, p. 224702, 2009.
[64] F. J. Pedrotti and L. S. Pedrotti, "Einstein's quantum theory of radiation," in Introduction to Optics, ed, 1992.
[65] H. Johnston. (2008). How lasers really work. Available: http://physicsworld.com/cws/article/news/2008/may/01/how-lasers-really-work
[66] S. Mujumdar, M. Ricci, R. Torre, and D. S.Wiersma, "Amplified extended modes in random lasers," Physical Review Letters, vol. 93, p. 053903, 2004.
[67] L. Rayleigh, "The problem of the whispering gallery," Philosophical Magazine, vol. 20, p. 1001, 1910.
[68] A. N. Oraevsky, "Whispering-gallery waves," Quantum Electronics, vol. 32, p. 377, 2002.
[69] M. Marhic, L. Kwan, and M. Epstein, "Whispering-gallery CO2-laser," IEEE Journal of Quantum Electronics, vol. 15, p. 487, 1979.
[70] J. Liu, S. Lee, Y. H. Ahn, J. Y. Park, K. H. Koh, and K. H. Park, "Identification of dispersion-dependent hexagonal cavity modes of an individual ZnO nanonail," Applied Physics Letters, vol. 92, p. 263102, 2008.
[71] 林麗娟. (1994). X光繞射原理及其應用. Available: http://www.materialsnet.com.tw/AD/ADImages/AAADDD/MCLM100/download/equipment/XR/TF-XRD/TF-XRD001.pdf
[72] A. P. Jephcoat, R. J. Henley, H. K. Mao, R. E. Cohen, and M. J. Mehl, "Raman spectroscopy and theoretical modeling of BeO at high pressure," Physical Review B, vol. 37, p. 4727, 1988.
[73] E. S. P. Leong, S. F. Yu, S. P. Lau, and A. P. Abiyasa, "Edge-emitting vertically aligned ZnO nanorods random laser on plastic substrate," IEEE Photonics Technology Letters, vol. 19, p. 1792, 2007.
[74] Y. Tian, X. Ma, L. Xiang, M. V. Ryzhkov, and A. A. Borodkin, "Optically and electrically pumped random lasing from ZnO films annealed at different temperatures," Optics Communications, vol. 285, p. 5323, 2012.
[75] S. H. Lee, T. Goto, H. Miyazaki, J. Chang, and T. Yao, "Optical resonant cavity in a nanotaper," Nano Letters, vol. 10, p. 2038, 2010.
[76] K. A. Alim, V. A. Fonoberov, M. Shamsa, and A. A. Balandin, "Micro-Raman investigation of optical phonons in ZnO nanocrystals," Journal of Applied Physics, vol. 97, p. 124313, 2005.
[77] C. T. Chien, M. C. Wu, C. W. Chen, H. H. Yang, J. J. Wu, W. F. Su, et al., "Polarization-dependent confocal Raman microscopy of an individual ZnO nanorod," Applied Physics Letters, vol. 92, p. 223102, 2008.
[78] R. Chen, H. D. Sun, T. Wang, K. N. Hui, and H. W. Choi, "Optically pumped ultraviolet lasing from nitride nanopillars at room temperature," Applied Physics Letters, vol. 96, p. 241101, 2010.
[79] C. Czekalla, C. Sturm, R. S. Grund, B. Cao, M. Lorenz, and M. Grundmann, "Whispering gallery mode lasing in zinc oxide microwires," Applied Physics Letters, vol. 92, p. 241102, 2008.
[80] R. Chen, B. Ling, X. W. Sun, and H. D. Sun, "Room temperature excitonic whispering gallery mode lasing from high-quality hexagonal ZnO microdisks," Advanced Materials, vol. 23, p. 2199, 2011.
[81] D. S. Wiersma, "The physics and applications of random lasers," Nature Physics, vol. 4, p. 359, 2008.