本實驗使用模版法來製備奈米結構，由於氧化鋅奈米柱製備方法簡單且成熟，所以選擇氧化鋅奈米柱來當作模版，實驗分為兩大部分，第一部分藉由控制種子層鍍製參數、種子層摻雜的比例和控制水熱法成長條件，製備出適合的模版，並探討柱體成長機制；第二部分利用射頻磁控濺鍍法，成功製備出鐵酸鉍/鎳酸鑭/氧化鋅奈米柱陣列核殼奈米柱結構。藉由導電式原子力顯微鏡量測單根奈米柱的電性，此結構在未極化之前，diode的行為並不明顯，在施加+10V的極化後，呈現明顯的diode的行為；施加-10V的極化後，則呈現反向diode行為。反向的外加電壓使靜電場方向反轉，表示此結構呈現可切換的diode特性，此現象為鐵電材料其內部極化可由外加電場反轉的特性。鐵酸鉍的電流傳導機制在正偏壓端為Pool-Frenkel emission，在負偏壓端電流傳導機制為Schottky emission，在柱體上方中心和旁邊量測的電性行為類似。PFM量測中，in-plane的訊號在施加±10V時明顯有些區塊變亮或變暗且±10V訊號對比正好相反，退回0V後，可觀察到有殘留極化的現象，表示此材料可以透過外加電壓使極化方向有所改變，且有殘留極化的現象，證明此材料擁有鐵電特性。

[1] Wang, J.; Neaton, J. B.; Zheng, H.; Nagarajan, V.; Ogale, S. B.; Liu, B.; Viehland, D.; Vaithyanathan, V.; Schlom, D. G.; Waghmare, U. V.; Spaldin, N. A.; Rabe, K. M.; Wuttig, M.; Ramesh, R., Epitaxial BiFeO3 multiferroic thin film heterostructures. Science 2003, 299 (5613), 1719.

[2] Yun, K. Y.; Noda, M.; Okuyama, M.; Saeki, H.; Tabata, H.; Saito, K., Structural and multiferroic properties of BiFeO3 thin films at room temperature. Journal of Applied Physics 2004, 96 (6), 3399.

[3] Yun, K. Y.; Ricinschi, D.; Kanashima, T.; Noda, M.; Okuyama, M., Giant ferroelectric polarization beyond 150 µC/cm2 in BiFeO3 thin film. Japanese Journal of Applied Physics Part 2-Letters & Express Letters 2004, 43 (5A), 647.

[4] Wang, J.; Li, M. Y.; Liu, X. L.; Pei, L.; Liu, J.; Yu, B. F.; Zhao, X. Z., Synthesis and Multiferroic Properties of BiFeO3 Nanotubes. Chinese Physics Letters 2009, 26 (11), 117301.

[5] Zhang, X. Y.; Lai, C. W.; Zhao, X.; Wang, D. Y.; Dai, J. Y., Synthesis and ferroelectric properties of multiferroic BiFeO3 nanotube arrays. Applied Physics Letters 2005, 87 (14), 143102.

[6] Zhang, X. Y.; Dai, J. Y.; Lai, C. W., Synthesis and characterization of highly ordered BiFeO3 multiferroic nanowire arrays. Progress in Solid State Chemistry 2005, 33 (2-4), 147.

[7] Chen, C.; Cheng, J. R.; Yu, S. W.; Che, L. J.; Meng, Z. Y., Hydrothermal synthesis of perovskite bismuth ferrite crystallites. J. Cryst. Growth 2006, 291 (1), 135.

[8] Lu, X. M.; Xie, J. M.; Song, Y. Z.; Lin, J. M., Surfactant-assisted hydrothermal preparation of submicrometer-sized two-dimensional BiFeO3 plates and their photocatalytic activity. Journal of Materials Science 2007, 42 (16), 6824.

[9] Zhang, X.; Bourgeois, L.; Yao, J.; Wang, H.; Webley, P. A., Tuning the morphology of bismuth ferrite nano- and microcrystals: From sheets to fibers. Small 2007, 3 (9), 1523.

[10] Hojamberdiev, M.; Xu, Y. H.; Wang, F. Z.; Wang, J.; Liu, W. G.; Wang, M. Q., Morphology-controlled hydrothermal synthesis of bismuth ferrite using various alkaline mineralizers. Ceramics-Silikaty 2009, 53 (2), 113.

[11] Baruah, S.; Dutta, J., Hydrothermal growth of ZnO nanostructures. Science and Technology of Advanced Materials 2009, 10 (1), 013001.

[12] Ahsanulhaq, Q.; Umar, A.; Hahn, Y. B., Growth of aligned ZnO nanorods and nanopencils on ZnO/Si in aqueous solution: growth mechanism and structural and optical properties. Nanotechnology 2007, 18 (11), 115603.

[13] Yim, K.; Kim, H. W.; Lee, C., Effects of annealing on structure, resistivity and transmittance of Ga doped ZnO films. Materials Science and Technology 2007, 23 (1), 108.

[14] Kim, S.; Lee, W. I.; Lee, E. H.; Hwang, S. K.; Lee, C., Dependence of the resistivity and the transmittance of sputter-deposited Ga-doped ZnO films on oxygen partial pressure and sputtering temperature. Journal of Materials Science 2007, 42 (13), 4845.

[15] Shin, S. W.; Sim, K. U.; Moon, J. H.; Kim, J. H., The effect of processing parameters on the properties of Ga-doped ZnO thin films by RF magnetron sputtering. Current Applied Physics 2010, 10, 274.

[16] Park, S. E.; Lee, J. C.; Song, P. K.; Lee, J. H., Properties of Gallium-Doped Zinc-Oxide Films Deposited by RF or DC Magnetron Sputtering with Various GZO Targets. Journal of the Korean Physical Society 2009, 54 (3), 1283.

[17] Liang, S.; Bi, X. F., Structure, conductivity, and transparency of Ga-doped ZnO thin films arising from thickness contributions. Journal of Applied Physics 2008, 104 (11), 113533.
[18] Qiu, J. J.; Li, X. M.; He, W. Z.; Park, S. J.; Kim, H. K.; Hwang, Y. H.; Lee, J. H.; Kim, Y. D., The growth mechanism and optical properties of ultralong ZnO nanorod arrays with a high aspect ratio by a preheating hydrothermal method. Nanotechnology 2009, 20 (15), 155603.

[19] Li, Q. W.; Bian, J. M.; Sun, J. C.; Wang, J. W.; Luo, Y. M.; Sun, K. T.; Yu, D. Q., Controllable growth of well-aligned ZnO nanorod arrays by low-temperature wet chemical bath deposition method. Applied Surface Science 2010, 256 (6), 1698.

[20] Ma, T.; Guo, M.; Zhang, M.; Zhang, Y. J.; Wang, X. D., Density-controlled hydrothermal growth of well-aligned ZnO nanorod arrays. Nanotechnology 2007, 18 (3), 035605.

[21] Wang, S. F.; Tseng, T. Y.; Wang, Y. R.; Wang, C. Y.; Lu, H. C.; Shih, W. L., Effects of preparation conditions on the growth of ZnO nanorod arrays using aqueous solution method. International Journal of Applied Ceramic Technology 2008, 5 (5), 419.

[22] Sugunan, A.; Warad, H. C.; Boman, M.; Dutta, J., Zinc oxide nanowires in chemical bath on seeded substrates: Role of hexamine. Journal of Sol-Gel Science and Technology 2006, 39 (1), 49.

[23] Zhou, Y.; Wu, W. B.; Hu, G. D.; Wu, H. T.; Cui, S. G., Hydrothermal synthesis of ZnO nanorod arrays with the addition of polyethyleneimine. Materials Research Bulletin 2008, 43 (8-9), 2113.

[24] Eerenstein, W.; Mathur, N. D.; Scott, J. F., Multiferroic and magnetoelectric materials. Nature 2006, 442 (7104), 759.

[25] Kittel C., Introduction to solid state physics. John Wiley &Sons, New York 1996, 7th ed.

[26] Burns G., Solid state physics. Academic Press, New York 1985

[27] Hill, N. A., Why are there so few magnetic ferroelectrics? Journal of Physical Chemistry B 2000, 104 (29), 6694.

[28] Haertling, G. H., Ferroelectric ceramics: History and technology. Journal of the American Ceramic Society 1999, 82 (4), 797.

[29] Dawber, M.; Rabe, K. M.; Scott, J. F., Physics of thin-film ferroelectric oxides. Reviews of Modern Physics 2005, 77 (4), 1083.

[30] Kingery W. D.; Bowen H. K.; Uhlmann D. R.,. Introduction to ceramics. John Wiley and Sons, New York 1976

[31] Lines M. E.; Glass A. M., Principles and application of ferroelectrics and related materials. Oxford University Press,New York 2001, Chap.2-5.

[32] Pabst, G. W.; Martin, L. W.; Chu, Y. H.; Ramesh, R., Leakage mechanisms in BiFeO3 thin films. Applied Physics Letters 2007, 90 (7), 072902.

[33] Chen, S. W.; Wu, J. M., Unipolar resistive switching behavior of BiFeO3 thin films prepared by chemical solution deposition. Thin Solid Films 2010, 519 (1), 499.

[34] Ruette, B.; Zvyagin, S.; Pyatakov, A. P.; Bush, A.; Li, J. F.; Belotelov, V. I.; Zvezdin, A. K.; Viehland, D., Magnetic-field-induced phase transition in BiFeO3 observed by high-field electron spin resonance: Cycloidal to homogeneous spin order. Physical Review B 2004, 69 (6), 064114.

[35] Liu, K.; Fan, H. Q.; Ren, P. R.; Yang, C., Structural, electronic and optical properties of BiFeO3 studied by first-principles. Journal of Alloys and Compounds 2011, 509 (5), 1901.

[36] Teague, J. R.; Gerson, R.; James, W. J., Dielectric hysteresis in single crystal BiFeO3. Solid State Communications 1970, 8 (13), 1073.

[37] Kumar, M. M.; Palkar, V. R.; Srinivas, K.; Suryanarayana, S. V., Ferroelectricity in a pure BiFeO3 ceramic. Applied Physics Letters 2000, 76 (19), 2764.

[38] Morozov, M. I.; Lomanova, N. A.; Gusarov, V. V., Specific features of BiFeO3 formation in a mixture of bismuth(III) and iron(III) oxides. Russian Journal of General Chemistry 2003, 73 (11), 1676.

[39] Wang, Y. P.; Zhou, L.; Zhang, M. F.; Chen, X. Y.; Liu, J. M.; Liu, Z. G., Room-temperature saturated ferroelectric polarization in BiFeO3 ceramics synthesized by rapid liquid phase sintering. Applied Physics Letters 2004, 84 (10), 1731.

[40] Roginska.Ye; Tomashpo.Yy; Venevtse.Yn; Petrov, V. M.; Zhdanov, G. S., Nature of dielectric and magnetic properties of BiFeO3. Soviet Physics Jetp-Ussr 1966, 23 (1), 47.

[41] Li, J. F.; Wang, J. L.; Wuttig, M.; Ramesh, R.; Wang, N.; Ruette, B.; Pyatakov, A. P.; Zvezdin, A. K.; Viehland, D., Dramatically enhanced polarization in (001), (101), and (111) BiFeO3 thin films due to epitiaxial-induced transitions. Applied Physics Letters 2004, 84 (25), 5261.

[42] Smith, R. T.; Achenbac.Gd; Gerson, R.; James, W. J., Dielectric properties of solid solutions of BiFeO3 with Pb(Ti,Zr)O3 at high temperature. Journal of Applied Physics 1968, 39 (1), 70.

[43] Ueda, K.; Tabata, H.; Kawai, T., Coexistence of ferroelectricity and ferromagnetism in BiFeO3-BaTiO3 thin films at room temperature. Applied Physics Letters 1999, 75 (4), 555.

[44] Qi, X. D.; Dho, J.; Tomov, R.; Blamire, M. G.; MacManus-Driscoll, J. L., Greatly reduced leakage current and conduction mechanism in aliovalent-ion-doped BiFeO3. Applied Physics Letters 2005, 86 (6), 062903.

[45] Popov, Y. F.; Zvezdin, A. K.; Vorobev, G. P.; Kadomtseva, A. M.; Murashev, V. A.; Rakov, D. N., Linear magnetoelectric effect and phase-transitions in bismuth ferrite, BiFeO3. Jetp Letters 1993, 57 (1), 69.

[46] Choi, T.; Lee, S.; Choi, Y. J.; Kiryukhin, V.; Cheong, S. W., Switchable Ferroelectric Diode and Photovoltaic Effect in BiFeO3. Science 2009, 324 (5923), 63.

[47] Yang, S. Y.; Martin, L. W.; Byrnes, S. J.; Conry, T. E.; Basu, S. R.; Paran, D.; Reichertz, L.; Ihlefeld, J.; Adamo, C.; Melville, A.; Chu, Y. H.; Yang, C. H.; Musfeldt, J. L.; Schlom, D. G.; Ager, J. W.; Ramesh, R., Photovoltaic effects in BiFeO3. Applied Physics Letters 2009, 95 (6), 062909.

[48] Yang, S. Y.; Seidel, J.; Byrnes, S. J.; Shafer, P.; Yang, C. H.; Rossell, M. D.; Yu, P.; Chu, Y. H.; Scott, J. F.; Ager, J. W.; Martin, L. W.; Ramesh, R., Above-bandgap voltages from ferroelectric photovoltaic devices. Nature Nanotechnology 2010, 5 (2), 143.

[49] Ji, W.; Yao, K.; Liang, Y. C., Bulk Photovoltaic Effect at Visible Wavelength in Epitaxial Ferroelectric BiFeO3 Thin Films. Advanced Materials 2010, 22 (15), 1763.

[50] Yuan, G. L.; Wang, J. L., Evidences for the depletion region induced by the polarization of ferroelectric semiconductors. Applied Physics Letters 2009, 95 (25), 252904.

[51] Qin, M.; Yao, K.; Liang, Y. C., High efficient photovoltaics in nanoscaled ferroelectric thin films. Applied Physics Letters 2008, 93 (12), 122904.

[52] Yao, K.; Gan, B. K.; Chen, M. M.; Shannigrahi, S., Large photo-induced voltage in a ferroelectric thin film with in-plane polarization. Applied Physics Letters 2005, 87 (21), 212906.

[53] Chen, S. W.; Lee, C. C.; Chen, M. T.; Wu, J. M., Synthesis of BiFeO3/ZnO core-shell hetero-structures using ZnO nanorod positive templates. Nanotechnology 2011, 22 (11), 115605.

[54] Chen, S. W.; Wu, J. M., Nucleation mechanisms and their influences on characteristics of ZnO nanorod arrays prepared by a hydrothermal method. Acta Materialia 2011, 59 (2), 841.
[55] Kumar, A.; Rai, R. C.; Podraza, N. J.; Denev, S.; Ramirez, M.; Chu, Y. H.; Martin, L. W.; Ihlefeld, J.; Heeg, T.; Schubert, J.; Schlom, D. G.; Orenstein, J.; Ramesh, R.; Collins, R. W.; Musfeldt, J. L.; Gopalan, V., Linear and nonlinear optical properties of BiFeO3. Applied Physics Letters 2008, 92 (12), 121915.

[56] Joshi, U. A.; Jang, J. S.; Borse, P. H.; Lee, J. S., Microwave synthesis of single-crystalline perovskite BiFeO3 nanocubes for photoelectrode and photocatalytic applications. Applied Physics Letters 2008, 92 (24), 242106.

[57] Chen, X. Y.; Yu, T.; Gao, F.; Zhang, H. T.; Liu, L. F.; Wang, Y. M.; Li, Z. S.; Zou, Z. G.; Liu, J. M., Application of weak ferromagnetic BiFeO3 films as the photoelectrode material under visible-light irradiation. Applied Physics Letters 2007, 91 (2), 022114.

[58] Yang, H.; Wang, Y. Q.; Wang, H.; Jia, Q. X., Oxygen concentration and its effect on the leakage current in BiFeO3 thin films. Applied Physics Letters 2010, 96 (1), 012909.

[59] Basu, S. R.; Martin, L. W.; Chu, Y. H.; Gajek, M.; Ramesh, R.; Rai, R. C.; Xu, X.; Musfeldt, J. L., Photoconductivity in BiFeO3 thin films. Applied Physics Letters 2008, 92 (9), 091905.

[60]Wang, C.; Jin, K. J.; Xu, Z. T.; Wang, L.; Ge, C.; Lu, H. B.; Guo, H. Z.; He, M.; Yang, G. Z., Switchable diode effect and ferroelectric resistive switching in epitaxial BiFeO3 thin films. Applied Physics Letters 2011, 98 (19), 192901.

[61]Robertson, J.; Chen, C. W., Schottky barrier heights of tantalum oxide, barium strontium titanate, lead zirconate titanate and strontium bismuth tantalate. Applied Physics Letters 1999, 74 (8), 1168

[62]Clark, S. J.; Robertson, J., Band gap and Schottky barrier heights of multiferroic BiFeO3. Applied Physics Letters 2007, 90 (13), 132903.

[63] Balke, N.; Bdikin, I.; Kalinin, S. V.; Kholkin, A. L., Electromechanical Imaging and Spectroscopy of Ferroelectric and Piezoelectric Materials: State of the Art and Prospects for the Future. Journal of the American Ceramic Society 2009, 92 (8), 1629.