1. 서론
n-ZnO 반도체 나노배열은 3.37 eV의 와이드 밴드 갭, 상온에서 60 meV의 큰 엑시톤 바인딩 에너지, 근자외선(near-UV) 방출, 압전특성(piezoelectricity)같은 우수한 성질 때문에 큰 관심을 불러 일으키고 있다. 그것들은 표면 어쿠스틱 웨이브 필터, 자외선 레이저장치, 포토닉 크리스탈, 포토 디텍터(photo detectors), 필드 이미팅(emitting) 장치, 센서, 압전특성 물체, 솔라셀 전극과 같은 폭넓은 첨단 기술 분야에서 중요한 구조적 산화(oxide) 나노 구조물로 여겨졌다. 나노로드, 나노튜브, 나노와이어, 나노콤(nanocomb), 나노시트와 같이 다른 형태를 지닌 ZnO 나노크리스탈이 개발되어 졌다. 지금까지 몇몇 기술들이 주로 양극(anodic) 알루미나 산화물(AAO) 템플릿, 기상 이동법(vapor phase transport(VPT)), 화학 기상 증착법(chemical vapor deposition), 펄스 레이저 증착법(pulsed laser dposion(PLD)), 스퍼터링(sputtering), 수용액(aqueous solution) 방법을 포함하여 ZnO 나노스케일 배열을 조합하기 위해 활용 되어졌다.
수용액 접근법은 성장온도가 100℃ 이하를 갖는 단순한 솔루션 방법이며 대면적으로 배열된 ZnO나노구조물을 얻을수 있는 방법이다.
ZnO 나노로드와 나노와이어는 Zn(NO3)2․6H2O/C6H12N4와 함께 전구체(precursor)로서 수용액에서 합성된다. Li 등은 성장시간에 증가에 의해 솔루션에서 나노로드의 위 표면에 형성된 나노튜브를 보고하였다. 그리고 그들은 나노튜브가 질소(nitrogen)를 함유한 화합물(compound)로부터 유도되었다고 제안하였다. 뿐만 아니라, ZnO 나노로드, 나노와이어, 프리즘들은 과포화된 Zn(NO3)2․6H2O/NaOH 솔루션에서 조합이 되었고, 큰 종횡비(aspect ratio)(30-40)가 EDA와 알코올을 더함으로써 달성이 가능했다. Yu 등은 5% 포마미드(formamide) 수용액의 아연 박편(foil)에서 ZnO 나노로드와 나노튜브를 합성했고, 형태 변화가 나노 구조물의 위부분에 가까운 곳에 아연 수렴물을 아래로 놓을 때에 가능했다. ZnO 나노튜브와 관 모양의 위스커(whisker)들은 PEG(2000)의 도움을 받아 Zn(NO3)2․6H2O/NH3․H2O를 사용함으로써 자랐으며, 조각 조각나는 일부 결정과 함께 나노로드들은 ZnCl2, C6H12N4와 NH3로 구성된 수용액에서 관찰 되었다.
· [1] D.M. Bagnall, Y.F. Chen, Z. Zhu, T. Yao, S. Koyama, M.Y. Shen, T. Goto, Optically pumped lasing of ZnO at room temperature, Appl. Phys. Lett. 70 (1997) 2230-2232
· [2] X.D. Bai, P.X. Gao, Z.L. Wang, E.G. Wang, Dual-mode mechanical
· resonance of individual ZnO nanobelts, Appl. Phys. Lett. 82 (2003)
· 4806-4808.
· [3] J.B. Lee, H.J. Kim, S.G. Kim, C.S. Hwang, S.H. Hong, Y.H. Shin, N.H.
· Lee, Deposition of ZnO thin films by magnetron sputtering for a film bulk
· acoustic resonator, Thin Solid Films 435 (2003) 179-185.
· [4] M. Zamfirescu, A. Kavokin, B. Gil, G. Malpuech, M. Kaliteevski, ZnO as
· a material mostly adapted for the realization of room-temperature polariton
· lasers, Phys. Rev. B 65 (2002), 161205(1-4).
· [5] Y. Wu, H. Yan, M. Huang, B. Messer, J.H. Song, P. Yang, Inorganic
· semiconductor nanowires: rational growth, assembly, and novel properties,
· Chem. Eur. J. 8 (2002) 1260-1268.
· [6] Y.F. Mestre, L.L. Zamora, J.M. Calatayud, Flow-chemiluminescence: a
· growing modality of pharmaceutical analysis, Luminescence 16 (2001) 213-235.
· [7] C.J. Lee, T.J. Lee, S.C. Lyu, Y. Zhang, H. Ruh, H.J. Lee, Field emission
· from well-aligned zinc oxide nanowires grown at low temperature, Appl.
· Phys. Lett. 81 (2002) 3648-3650.
· [8] Q. Wan, Q.H. Li, Y.J. Chen, T.H. Wang, X.L. He, J.P. Li, C.L. Lin,
· Fabrication and ethanol sensing characteristics of ZnO nanowire gas
· sensors, Appl. Phys. Lett. 84 (2004) 3654-3656.
· [9] Z.L. Wang, J.H. Song, Piezoelectric nanogenerators based on zinc oxide
· nanowire arrays, Science 412 (2006) 242-246.
· [10] C. Levy-Clement, R. Tena-Zaera, M.A. Ryan, A. Katty, G. Hodes, CdSesensitized
· p-CuSCN/nanowire n-ZnO heterojunctions, Adv. Mater. 17
· (2005) 1512-1515.
· [11] Y. Sun, G.M. Fuge, N.A. Fox, D.J. Riley, M.N.R. Ashfold, Synthesis of
· aligned arrays of ultrathin ZnO nanotubes on a Si wafer coated with a thin
· ZnO film, Adv. Mater. 17 (2005) 2477-2481.
· [12] J.B. Baxter, E.S. Aydil, Epitaxial growth of ZnO nanowires on a- and cplane
· sapphire, J. Cryst. Growth 274 (2005) 407-411.
· [13] J.H. Park, Y.J. Choi, J.G. Park, Evolution of nanowires, nanocombs, and
· nanosheets in oxide semiconductors with variation of processing conditions,
· J. Eur. Ceram. Soc. 25 (2005) 2037-2040.
· [14] Z. Fang, Y. Wang, X. Peng, X. Liu, C. Zhen, Structural and optical
· properties of ZnO films grown on the AAO templates, Mater. Lett. 57
· (2003) 4187-4190.
· [15] Z. Zhang, H. Yu, X. Shao, M. Han, Near-room-temperature production of
· diameter-tunable ZnO nanorod arrays through natural oxidation of zinc
· metal, Chem. Eur. J. 11 (2005) 3149-3154.
· [16] J.-J. Wu, S.-C. Liu, Low-temperature growth of well-aligned ZnO nanorods
· by chemical vapor deposition, Adv. Mater. 14 (2002) 215-218.
· [17] Y. Sun, G.M. Fuge, M.N.R. Ashfold, Growth of aligned ZnO nanorod
· arrays by catalyst-free pulsed laser deposition methods, Chem. Phys. Lett.
· 396 (2004) 21-26.
· [18] R. AlAsmar, G. Ferblantier, F. Mailly, A. Foucaran, Structural and optical
· properties of ZnO fabricated by reactive e-beam and rf magnetron
· sputtering techniques, Phys. Stat. Sol. C 2 (2005) 1331-1335.
· [19] K. Govender, D.S. Boyle, P. O`Brien, D. Binks, D. West, D. Coleman,
· Room-temperature lasing observed from ZnO nanocolumns grown by
· aqueous solution deposition, Adv. Mater. 14 (2002) 1221-1224.
· [20] L. Vayssieres, Growth of arrayed nanorods and nanowires of ZnO from
· aqueous solutions, Adv. Mater. 15 (2003) 464-466.
· [21] X. Liu, Z. Jin, S. Bu, J. Zhao, K. Yu, Preparation of ZnO nanorods and
· special lath-like crystals by aqueous chemical growth (ACG) method,
· Mater. Sci. Eng. B 129 (2006) 139-143.
· [22] Q. Li, V. Kumar, Y. Li, H. Zhang, T.J. Marks, R.P.H. Chang, Fabrication of
· nanorods and nanotubes in aqueous solutions, Chem. Mater. 17 (2005)
· 1001-1006.
· [23] R. Peterson, C. Fields, B. Gregg, Epitaxial chemical deposition of ZnO
· nanocolumns from NaOH solutions, Langmuir 20 (2004) 5114-5118.
· [24] D. Wang, C. Song, Controllable synthesis of ZnO nanorod and prism
· arrays in a large area, J. Phys. Chem. B 109 (2005) 12697-12700.
· [25] B. Liu, H.C. Zeng, Hydrothermal synthesis of ZnO nanorods in the
· diameter regime of 50 nm, J. Am. Chem. Soc. 125 (2003) 4430-
· 4431.
· [26] H. Yu, Z. Zhang, M. Han, X. Hao, F. Zhu, A general low-temperature route
· for large-scale fabrication of highly oriented ZnO nanorod/nanotube
· arrays, J. Am. Chem. Soc. 127 (2005) 2378-2379.
· [27] J. Duan, X. Huang, E. Wang, PEG-assisted synthesis of ZnO nanotubes,
· Mater. Lett. 60 (2006) 1918-1921.
· [28] J. Liu, X. Huang, A low-temperature synthesis of ultraviolet-light-emitting
· ZnO nanotubes and tubular whiskers, J. Solid State Chem. 179 (2006)
· 843-848.
· [29] Y. Gao, M. Nagai, Morphology evolution of ZnO thin films from aqueous
· solutions and their application to solar cells, Langmuir 22 (2006) 3936-
· 3940.
· [30] Y. Tak, K. Yong, Controlled growth of well-aligned ZnO nanorod array
· using a novel solution method, J. Phys. Chem. B 109 (2005) 19263-19269.
· [31] S. Yamabi, H. Imai, Growth conditions for wurtzite zinc oxide films in
· aqueous solutions, J. Mater. Chem. 12 (2002) 3773-3778.
· [32] W.J. Li, E.W. Shi, W.Z. Zhong, Z.W. Yim, Growth mechanism and
· growth habit of oxide crystals, J. Cryst. Growth 203 (1999) 186-196.
· [33] X. Liu, Z. Jin, S. Bu, J. Zhao, Z. Liu, Growth of ZnO films with controlled
· morphology by aqueous solution method, J. Am. Ceram. Soc. 89 (2006)
· 1226-1231.