氮化鎵為一寬能隙且直接能隙的半導體材料，其能隙3.4 eV，屬於紫外光，然而可製備為三元化合物，光範圍可調控在可見光，其主要應用於發光二極體、雷射光源與高功率電晶體。
此研究以低溫成長氮化鎵奈米線為主軸，其中也發現金觸媒的遷移現象。低溫成長氮化鎵奈米線，成長溫度介於550 ℃～700 ℃。成長奈米線時VLS與VS機制將同時發生，此為一競爭反應。成長過程中，VLS機制為主，而低溫製程時VS成長變為較顯著。由於高溫時，鎵在奈米線表面移動的平均自由路徑較長，易移動至觸媒或缺陷處再反應，因此高溫成長時奈米線側壁很平滑；反之，低溫成長時，鎵的移動平均自由路徑短，未能移動至最低能量處而被活化的氮反應，使得奈米線表面不平整。
觸媒的遷移與氣相鎵濃度有關，當鎵濃度越高金觸媒越容易從奈米線頂端往下遷移。由於高濃度的鎵將使奈米線的表面沈積連續的鎵原子層，並使金觸媒形成飽和狀態的金鎵合金，使得金觸媒易經由鎵原子層，持續在奈米線側壁進行移動，當金觸媒在側壁移動時，也可能再次進行VLS成長形成枝狀奈米線。

Gallium Nitride nanowire preparation is typically based on the vapor-liquid-solid (VLS) or vapor-solid-solid (VSS) growth mechanism and involves the use of catalysts such as Au, Ni, Fe, or In. Nanowires composed of GaN and related group III-N alloys have a huge potential for light-emitting devices, laser, and high power transistors. The bandgap of GaN is 3.4 eV that be emitting the ultraviolet light. Therfore, ternary compound of GaN will be radiating at range of visible light.
In this research, the main subject is focused on growing GaN nanowires at low temperature. Moreover, during experiment, we found out the phenomenon, which is migration of gold catalyst from top to bottom of nanowires. For the growth of GaN nanowires at low temperature, the range of temperature are between 550 and 700 ℃, and the competitive reaction will take place between VLS and VS mechanism. During the growth of GaN nanowires, the process is based on VLS growth mechanism, and VS growth mechanism will become more outstanding at low temperature than high temperature. Gallium atoms, which will migrate to the catalysts or defects on nanowires sidewall, so the sidewalls are smooth, are longer mean free path at high temperature. On the contrary, the rough sidewalls take place at low temperature.
The migration of gold catalyst that migrates from top to bottom of nanowires is related to gallium concentration in gas phase. On high gallium concentration, the gallium atoms will deposit on the nanowires sidewall and then form the continuous film, which is about several atoms layer. After gallium depositing into catalyst, gold will become gallium-gold alloy that migrates from top to bottom by way of the several gallium atoms layer. During migrating on the sidewall, the alloy will grow on sidewall to form branch structure.

[1] D. M. Eigler and E. K. Schweizer, Nature, 344, 524 (1990).
[2] M. F. Crommie, C. P. Lutz and D. M. Eigler, Science, 262, 218 (1993).
[3] S. Iijima, Nature, 354, 56 (1991).
[4] C. V. Nguyen, C. So, R. M. Stevens, Y. Li, L. Delziet, P. Sarrazin, and M. Meyyappan, J. Phys. Chem. B, 108, 2816 (2004).
[5] G. E. Moore, Electronics, 38 (1965).
[6] Y. Wu and P. Yang, J. Am. Chem. Soc. 123, 3165 (2001).
[7] R. S. Wagner Whisker Technology, Wiley-Interscience, New York (1970)
[8] S. T. Lee, N. Wang, Y. F. Zhang and Y. H. Tang, MRS Bull. 24, 36 (1999).
[9] B. Gates, B. Mayers, B. Cattle and Y. Xia, Adv. Funct. Mater. 12, 219 (2002).
[10] B. Messer, J. H. Song, M. Huang, Y. Wu, F. Kim and P. Yang, Adv. Mater. 12, 1526(2000).
[11] M. Zheng, L. Zhang, X. Zhang, J. Zhang and G. Li, Chem. Phys. Lett. 334, 298 (2001).
[12] T. J. Trentler, K. M. Hickman, S. C. Geol, A. M. Viano, P. C. Gibbons and W E Buhro, Science 270, 1791 (1995).
[13] S. H. Yu, J. Yang, Z. H. Han, R. Y. Yang, Y. T. Qian and Y. H. Zhang, J. Solid State Chem. 147, 637 (1999).
[14] Y. Xia, P. Yang, Y. Sun, Y. Wu, B. Mayer, B. Gates, Y. Ying, F. Kim, H. Yan, Adv. Mater. 15, 253 (2003).
[15] S. Nakamura, Y. Harada and M. Seno, Appl. Phys. Lett. 58, 2021 (1991).
[16] V. W. L. Chin, T. L. Tansely and T. Osotchan, J. Appl. Phys. 75, 7365 (1994).
[17] S. Gwo, C. L. Wu, C. H. Shen, H. W. Lin, H. Y. Chen and H. Ahn, Proc. of SPIE, 6134, 61340L-1 (2006).
[18] J. G. Lozano, F. M. Morales, R. Garcia, D. Gonzalez, V. Lebedev, C. Y. Wang, V. Cimalla and O. Ambacher, Appl. Phys. Lett. 90, 091901 (2007).
[19] Z. G. Qian, W. Z. Shen, H. Ogawa and Q. X. Guo, J. Phys.: Condens. Matter, 16, R381 (2004).
[20] S. N. Mohammad and H. Morkoc, Prog. Quant. Electron. 20, 361 (1996).
[21] B. E. Foutz, S. K. O’Leary, M. S. Shur and L. F. Eastman, J. Appl. Phys. 85, 7727 (1999).
[22] R. Ascazubi, I. Wilke, K. Denniston, H. Lu and W. J. Schaff, Appl. Phys. Lett. 84, 4810 (2004).
[23] S. K. Pugh, D. J. Dugdale, S. Brand and R. A. Abram, Semicond. Sci. Technol. 14, 23 (1999).
[24] M. Yoshimoto, H. Yamamoto, W. Huang, H. Harima, J. Saraie, A. Chayahara and Y. Horino, Appl. Phys. Lett. 83, 3480 (2003).
[25] A. G. Bhuiyan, K. Sugita, K. Kasashima, A. Hashimoto, A. Yamamoto and V. Yu Davydov, Appl. Phys. Lett. 83, 4788 (2003).
[26] J. Wu, W. Walukiewicz, K. M. Yu, J. W. Ager III, E. E. Haller, H. Lu, W. J. Schaff, Y. Saito and Y. Nanishi, Appl. Phys. Lett. 80, 3967 (2002).
[27] H. Lu, W. J. Schaff, J. Hwang, H. Wu, G. Koley and L. F. Eastman, Appl. Phys. Lett. 79, 1489 (2001).
[28] A. G. Bhuiyan, T. Tanaka, K. Kasashima, A. Hashimoto and A. Yamaoto, Jpn. J. Appl. Phys. 42, 7284 (2003).
[29] J. Aderhold, V. Yu Davydov, F. Fedler, D. Mistele, H. Klausing, T. Rotter, O. Semchinova, J. Stemmer and J. Graul, Proc. of SPIE, 4086, 82 (2000).
[30] J. Grandal, M. A. Sanchez-Garcı’ a, F. Calle and E. Calleja, Phys. Status Solidi (c), 2, 2289 (2005).
[31] A. G. Bhuiyan, A. Hashimoto and A. Yamamoto, J. Appl. Phys. 94, 2779 (2003).
[32] L. Liu, J. H. Edgar, Materials Science and Engineer, R37, 61 (2002).
[33] W. C. Johnson, J. B. Parson, and M. C. Crew, J. Phys. Chem., 36, 2529 (1932).
[34] S. Yoshida, S. Mwasawa, S. Gonda, Appl. Phys. Lett., 42, 427 (1983).
[35] S. Nakamura, Jpn. J. Appl. Phys., 30, 10 (1991).
[36] W. Li , A.Z. Li, M. Qi, Y.G. Zhang, Z.B. Zhao, Q.K. Yang, Mater. Sci. Eng. B-Solid State Mater. Adv. Technol., 75, 224-227 (2000).
[37] W. C. Hou, L. Y. Chen, Franklin C. N. Hong, Diam. Relat. Mat., 17, 1780-1784 (2008).
[38] R. S. Wanger and W. C. Ellis, Appl.Phys. Lett. 4, 89 (1964).
[39] X. F. Duan and C. M. Lieber, Adv. Mater. 12, 298 (2000).
[40] X. F. Duan and C. M. Lieber, J. Am. Chem. Soc. 122, 188 (2000).
[41] M. Yazawa, M. Koguchi, A. Muto, M. Ozawa and K. Hiruma, Appl. Phys. Lett. 61, 2051 (1992).
[42] A. M. Morales and C. M. Lieber, Science, 279, 208 (1998).
[43] M. H. Huang, Y. Wu, H. Feick, N. Tran, E. Weber and P. Yang, Adv. Mater. 13, 113 (2001).
[44] Y C Choi, W S Kim, Y S Park, S M Lee, D J Bae, Y H Lee, G-S Park, W B Choi, N S Lee and J M Kim, Adv. Mater. 12, 746 (2000).
[45] J. Hu, M. Ouyang, P. Yang and C. M. Lieber, Nature, 399, 48 (1999).
[46] H. Omi and T. Ogino, Appl. Phys. Lett. 71, 2163 (1997).
[47] A. B. Greytak, L. J. Lauhon, M. S. Gudiksen and C. M. Lieber, Appl. Phys. Lett. 84, 4176 (2004).
[48] S. H. Yun, A. Dibos, J. Z. Wu and D-K Kim, Appl. Phys. Lett. 84, 2892 (2004).
[49] D. Wang, J. G. Lu, C. J. Otten and W. E. Buhro, Appl. Phys. Lett. 83, 5280 (2003).
[50] C. C. Chen, C. C. Yeh, C. H. Chen, M. Y. Yu, H. L. Liu, J. J. Wu, K. H. Chen, L. C. Chen, J. Y. Peng and Y. F. Chen, J .Am. Chem. Soc. 123, 2791 (2001).
[51] Y. C. Zhu, Y. Bando, D. F. Xue and D. Golberg, Adv. Mater. 16, 631 (2004).
[52] Q. Li, X. Gong, C. Wang, J. Wang, K. ip, S. Hark, Adv. Mater. 16, 1436 (2004).
[53] C. Ye, G. Meng, Y. Wang, Z. Jiang, L. Zhang, J. Phys. Chem. B 106, 10338 (2002).
[54] K. W. Chang and J. J. Wu, J. Phys. Chem. B, 106, 7796 (2002).
[55] R. Hupta, Q. Xiong, G. D. Mahan and P. C. Eklund, Nano. Lett. 3, 1745 (2003).
[56] E. P. A. M. Bakkers and M. A. Verheijen, J. Am. Chem. Soc. 125, 3440 (2003).
[57] M. S. Gudisksen, J. Wang and C. M. Lieber, J. Phys. Chem. B 106, 4036 (2002).
[58] S. C. Lyu, Y. Zhnag, C. J. Lee, H. Ruh and H. J. Lee, Chem. Mater. 15, 3294 (2003).
[59] P. Gao and Z. L. Wang, J. Phys. Chem. B, 106, 12653 (2002).
[60] C. Tang, Y. Bando and T. Sato, J. Phys. Chem. B, 106, 7449 (2002).
[61] J. W. Hu, Q. Li, X. M. Meng, C. S. Lee and S. T. Lee, J. Phys. Chem. B 106, 9526 (2002).
[62] K. W. Chang and J. J. Wu, J. Phys. Chem. B, 108, 1838 (2004).
[63] Y. Wang, V. Schmidt, S. Senz and U. Gosele, Nature Nanotechnology, 1, 186 (2006)
[64] X. Weng, R. A. Burke and J. M. Redwing, Nanotechnology, 20, 085610 (2009)
[65] L. Geelhaar, C. Cheze, W. M. Weber, R. Averbeck, and H. Riechert, Appl. Phys. Lett., 91, 093113 (2007)
[66] W. C. Hou, L. Y. Chen, W. C. Tang, Franklin C. N. Hong, Crystal Growth of Design (Submit)
[67] L. V. Titova, Thang B. Hoang, H. E. Jackson, and L. M. Smith, Appl. Phys. Lstt., 89, 173126 (2006)
[68] J. R. Roth, "Industrial plasma engineering-Volume 1: Principles Institute of Physics", Publishing in London, (1995)
[69] D. B. Williams, A. B. Carter, Transmission Electron Microscopy, Plenum Press, New York, 1, 7 (1996)
[70] C. C. Chen and C. C. Yeh, Adv. Mater., 10, 12 (2000)
[71] T. B. Massalski, Binary Alloy Phase Diagrams, Ohio, 1, 260