本實驗為利用離子束能量8、12以及16 keV 沉積不同表面粗糙度的鋅薄膜，再以330、380、400以及420 ℃熱氧化成長氧化鋅奈米線。實驗結果發現只有在離子束能量為12 keV 所沉積的鋅薄膜在熱氧化溫度為400 ℃下條件下，才會有較多且均勻的氧化鋅奈米線產生。氧化鋅奈米線平均長度約為1 µm而其寬度約為~30 nm，氧化鋅奈米線其成長方向為[110]。室溫下氧化鋅奈米線的光激發光光譜顯示強的近能隙發光在377 nm，半高寬為95 meV，且無缺陷造成的可見光發光。場發射結果顯示氧化鋅奈米線其開啟電場為7.9 V/µm，場發射增強因子為691。經由實驗結果及文獻，顯示利用熱氧化金屬鋅成長氧化鋅奈米線其成長與氧化鋅內缺陷擴散有關，本文將會提出可能的氧化鋅奈米結構成長機制。

Metallic zinc films with various surface roughness were prepared by ion beam sputter deposition utilizing beam energy at 8, 12 and 16 keV and the zinc films were subject to thermal oxidation at 330 ~ 420 ℃. Experimental results show that thermal oxidation of metallic zinc films deposited by 12 keV ion beam at 400 ℃ results the highest density of ZnO nanowires. The ZnO nanowires were grown along the [110] direction and the average length and diameter of the ZnO nanowires were 1 um and 30 nm, respectively. Room temperature photoluminescence study shows a strong near-band-edge emission at 377 nm with a full-width-at-half maximum of 95 meV and negligible deep level emission. Field emission study shows a turn-on field of 7.9 V/um and a field enhancement factor of 691. A growth mechanism of the ZnO nannowire is proposed.

參考文獻

[1] W. K. Hong, B. J. Kim, T. W. Kim, G. Jo, S. Song, S. S. Kwon, A. Yoon, E. A. Stach, and T. Lee,“Electrical properties of ZnO nanowire field effect transistors by surface passivation,” Colloids Surf., A, Vol. 313-314, pp. 378-382, 2007.
[2] K. Keem, J. Kang, C. Yoon, D. Yeom, D. Y. Jeong, B. M. Moon, and S. Kim,“A fabrication technique for top-gate ZnO nanowires field-effect transistors by a photolithography process,” Microelectron. Eng., Vol. 84, pp. 1622-1626, 2007.
[3] Y. W. Zhu, H. Z. Zhang, X. C. Sun, S. Q. Feng, J. Xu, Q. Zhao, B. Xiang, R. M. Wang, and D. P. Yu,“Efficient field emission from ZnO nanoneedle arrays,” Appl. Phys. Lett., Vol. 83, No. 1, pp. 144-146, 2003.
[4] R. S. Wagner and W. C. Ellis,“Vapor-Liquid-Solid mechanism of single crystal growth,” Appl. Phys. Lett., Vol. 4, No. 5, pp. 89-90, 1964.
[5] W. I. Park, D. H. Kim, S.-W. Jung, and Gyu-Chul Yi,“Metalorganic vapor-phase epitaxial growth of vertically well-aligned ZnO nanorods,” Appl. Phys. Lett., Vol. 80, No. 22, pp. 4232-4234, 2002.
[6] Y. Gui, C. Xie, Q. Zhang, M. Hu, J. Yu, and Z. Weng,“Synthesis and characterization of ZnO nanostructure by two-step oxidation of Zn nano- and microparticles,” J. Cryst. Growth, Vol. 289, pp. 663-669, 2006.
[7] M. H. Hung, Y. Wu, H. Feick, N. Tran, E. Weber, and P. Yang,“Catalytic growth of zinc oxide nanowires by vapor transport,” Adv. Mater., Vol. 13, No. 2, pp. 113-116, 2001.
[8] S. N. Cha, B. G. Song, J. E. Jang, J. E. Jung, I. T. Han, J. H. Ha, J. P. Hong, D. J. Kang, and J. M. Kim,“Controlled growth of vertically aligned ZnO nanowires with different crystal orientation of the ZnO seed layer,” Nanotechnology, Vol. 19, pp. 235601-235604, 2008.
[9] Y. Chen, B. Qu, Y. A. Barnakov, Q. Tang, and J. Chen,“Microstructure studies of ZnO nanoneedles,” J. Mater. Sci. – Mater. Electron, Vol. 20, pp. 328-333, 2009.
[10] M. Grunze, W. Hirschwald, and D. Hofmann,“Zinc oxide: surface structure, stability and mechanisms of surface reactions,” J. Cryst. Growth, Vol. 52, pp. 241-249, 1981.
[11] A. Tsukazaki, A. Ohtomo, T. Onuma, M. Ohtani, T. Mankino, M. Sumiya, K. Ohtani, S. F. Chichibu, S. Fuke, Y. Segawa, H. Ohno, H. Koinuma, and M. Kawasaki,“Reported temperature modulation epitaxy for p-type doping and light-emitting diode based on ZnO,” Nat. Mater., Vol. 4, pp. 42-46, 2005.
[12] H. Rensmo, K. Keis, H. Lindstreöm, S. Södergren, A. Solbrand, A. Hagfeldt, S.E. Lindquist, L.N. Wang, and M. Muhammed,“High light-to-energy conversion efficiencies for solar cells based on nanostructured ZnO electrodes,” J. Phys. Chem. B, Vol. 101, pp. 2598-2601, 1997.
[13] 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.
[14] L. M. Li, C. C. Li, J. Zhang, Z. F. Du, B. S. Zou, H. C. Yu, Y. G. Wang, and T. H. Wang,“Bandgap narrowing and ethanol sensing properties of In-doped ZnO nanowires,” Nanotechnology, Vol. 18, pp. 225504-225507, 2007.
[15] H. D. Li, S. F. Yu, A. P. Abiyasa, C. Yuen, S. P. Lau, H. Y. Yang, and Eunice S. P. Leong.“Strain dependence of lasing mechanism in ZnO epilayer,” Appl. Phys. lett, Vol. 86, pp. 261111, 2005.
[16] E. A. Gulbransen, and T. P. Copan,“Microtopology of the surface reactions of oxygen and water vapour with metals,” Discuss. Faraday Soc., Vol. 28, pp. 229-233, 1959.
[17] S. Ren, Y. F. Bai, Jun Chen, S. Z. Deng, N. S. Xu, Q. B. Wu, and Shihe Yang,“Catalyst-free synthesis of ZnO nanowire arrays on zinc substrate by low temperature thermal oxidation,” Mater. Lett., Vol. 61, pp. 666-670, 2007.
[18] W. Yu, and C. Pan,“Low temperature thermal oxidation synthesis of ZnO nanoneedles and the growth mechanism,” Mater. Chem. Phys., Vol. 115, pp. 74-79, 2009.
[19] L. C. Chao, J. W. Lee, and C. C. Liau,“ZnO nanoneedles prepared by ion implantation and thermal oxidation on metallic zinc foils,” J. Phys. D: Appl. Phys., Vol. 41, pp. 115405-115409, 2008.
[20] N. Cabrera, and N. F. Mott,“Theory of the oxidation of metals,” Rep. Prog. Phys., Vol. 12, pp. 163-184, 1949.
[21] R. H. Fowler and L. W. Nordheim,“Electron emission in intense electric fields,” Proc. R. Soc. London A., Vol. 119, pp. 173-181, 1928.
[22] D. B. Medved,“Photoconductivity and chemisorption kinetics in sintered zinc oxide semiconductor,” J. Phys. Chem. Solids, Vol. 20, pp. 255-267, 1961.
[23] W. Gopel,“Oxygen interaction of stoichiometric and non- stoichiometric ZnO prismatic surfaces,” Surf. Sci., Vol. 62, pp. 165-182, 1977.
[24] W. H. Hirschwald,“Zinc oxide: an outstanding example of a binary compound semiconductor,” Acc. Chem. Res., Vol. 18, pp. 228-234, 1985.
[25] T. Asokan, and R. Freer,“Grain and grain boundary conduction in zinc oxide varistors before and after DC degradation,” J. Eur. Ceram. Soc., Vol. 11, pp. 545-550, 1993.
[26] B. J. Wuensch, and H. L. Tuller,“Lattice diffusion, grain boundary diffusion and defect structure of ZnO,” J. Phys. Chem. Solids, Vol. 55, No. 10, pp. 975-984, 1994.
[27] N. Wang, K. K. Fung, S. Wang, and S. Yang,“Oxide-assisted nucleation and growth of copper sulphide nanowire arrays,” J. Cryst. Growth, Vol. 233, pp. 226-232, 2001.
[28] 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, 2009.
[29] N. Fujimura, T. Nishihara, S. Goto, J. Xu, and T. Ito,“Control of preferred orientation for ZnOx film: control of self-texture,” J. Cryst. Growth, Vol. 130, pp. 269-279, 1993.
[30] I. Shalish, H. Temkin, and V. Narayanamurti,“Size-dependent surface luminescence in ZnO nanowires,” Phys. Rev. B, Vol. 69, pp. 245401, 2004.