Abstract
Dense and vertically aligned ZnO–ZnGa2O4 core–shell nanowires were synthesized in large scale on a-plane sapphire substrates by a simple two-step chemical vapor deposition method. The synthesized ZnO–ZnGa2O4 core–shell nanowires were connected through their base by a thick underlayer of the same material realizing electrical contact of the nanostructured array. X-ray diffraction and transmission electron microscopy analyses of the core–shell nanowires reveal that the ZnO cores and ZnGa2O4 shells of the core–shell nanowires are of single-crystal quality and have aligned crystallographic orientations. The ultraviolet–visible diffuse reflectance spectra of the core–shell nanowires showed two sharp edges corresponding to near-band-edge absorption contributed by the ZnO cores and the ZnGa2O4 shells. Moreover, the room-temperature photoluminescence spectra of the core–shell nanowires gave three UV emission peaks coming from the ZnGa2O4 shells and the ZnO cores. The dense and vertically aligned ZnO–ZnGa2O4 core–shell nanowires showing promising photoelectric properties offer an ideal structure for light harvesting applications such as a photoanode in a photoelectrochemical water splitting cell.
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Bakkers EPAM, Dam JAV, Franceschi SD, Kouwenhoven LP, Kaiser M, Verheijen M, Wondergem H, Sluis PAD (2004) Epitaxial growth of InP nanowires on germanium. Nat Mater 3:769–773
Cao BB, Chen J, Huang R, Ikuhara Y, Hirayama T, Zhou W (2011) Axial growth of Zn2GeO4/ZnO nanowire heterojunction using chemical vapor deposition. J Cryst Growth 316:46–50
Chang K, Wu J (2005) Formation of well-aligned ZnGa2O4 nanowires from Ga2O3/ZnO core-shell nanowires via a Ga2O3/ZnGa2O4 epitaxial relationship. J Phys Chem B 109:13572–13577
Du X, Zhu Y, Yang T, Shen Y, Zeng Y, Xu F (2009) Synthesis and morphology evolution of GaN/C nanocables. J Nanopart Res 11:1179–1183
Fan HJ, Werner P, Zacharias M (2006) Semiconductor nanowires: from self-organization to patterned growth. Small 2:700–717
Fan HJ, Yang Y, Zacharias M (2009) ZnO-based ternary compound nanotubes and nanowires. J Mater Chem 19:885–900
Han W, Zhang Y, Nam C, Black CT, Mendez EE (2010) Growth and electronic properties of GaN/ZnO solid solution nanowires. Appl Phys Lett 97:083108–083111
Hannon JB, Kodambaka S, Ross FM, Tromp RM (2006) The influence of the surface migration of gold on the growth of silicon nanowires. Nature 440:69–71
Huang YJ, Boukai A, Yang PD (2009) High density n-Si/n-TiO2 core/shell nanowire arrays with enhanced photoactivity. Nano Lett 9:410–415
Ikarashi K, Sato J, Kobayashi H, Saito N, Nishiyama H, Inoue Y (2002) Photocatalysis of water decomposition by RuO2–dispersed ZnGa2O4 with d10 configuration. J Phys Chem B 106:9048–9053
Kim JS, Kang HI, Kim WN, Kim JI, Choi JC, Park HL, Kim GC, Kim TW, Huang YH, Mho SI, Jun MC, Han M (2003) Color variation of ZnGa2O4 phosphor by reduction-oxidation processes. Appl Phys Lett 82:2029–2031
Kumagai N, Ni L, Irie H (2011) Visible-light-sensitive water-splitting photocatalyst composed of Rh3+ in a 4d6 electronic configuration, Rh3+-doped ZnGa2O4. Chem Commun 47:1884–1886
Lauhon LJ, Gudiksen MS, Wang D, Lieber CM (2002) Epitaxial core-shell and core-multishell nanowire heterostructures. Nature 420:57–61
Li YJ, Lu Y, Wang CW, Li KM, Chen LJ (2006) ZnGa2O4 nanotubes with sharp cathodoluminescence peak. Appl Phys Lett 88(143102):1–3
Maeda K, Takata T, Hara M, Saito N, Inoue Y, Kobayashi H, Momen K (2005) GaN:ZnO solid solution as a photocatalyst for visible-light-driven overall water splitting. J Am Chem Soc 127:8286–8287
Roth AP, Webb JB, Williams DF (1982) Band-gap narrowing in heavily defect-doped ZnO. Phys Rev B 25:7836–7839
Shu Q, Wei J, Wang K, Zhu H, Li Z, Jia Y, Gui X, Guo N, Li X, Ma C, Wu D (2009) Hybrid heterojunction and photoelectrochemistry solar cell based on silicon nanowires and double-walled carbon nanotubes. Nano Lett 9:4338–4342
Soci C, Zhang A, Xiang B, Dayeh SA, Aplin DPR, Park J, Bao XY, Lo YH, Wang D (2007) ZnO nanowire UV photodetectors with high internal gain. Nano Lett 7:1003–1009
Thelander C, Agarwal P, Brongersma S, Eymery J, Feiner LF, Forchel A, Scheffler M, Riess W, Ohlsson BJ, Gosele U, Samuelson L (2006) Nanowire-based one-dimensional electronics. Mater Today 9:28–35
Vanheusden K, Warren WL, Seager CH, Tellant DR, Voigt JA, Gnade BE (1996) Mechanisms behind green photoluminescence in ZnO phosphor powders. J Appl Phys 79:7983–7990
Walsh A, Silva JLFD, Wei S (2008) Origins of band-gap renormalization in degenerately doped semiconductors. Phys Rev B 78:075211 1–075211 5
Wang K, Chen J, Zhou W, Zhang Y, Yan Y, Pern J, Mascarenhas A (2008) Direct growth of highly mismatched type II ZnO/ZnSe core/shell nanowire arrays on transparent conducting oxide substrates for solar cell applications. Adv Mater 20:3248–3253
Wu XL, Siu GG, Fu CL, Ong HC (2001) Photoluminescence and cathodoluminescence studies of stoichiometric and oxygen-deficient ZnO films. Appl Phys Lett 78:2285–2287
Yang PD, Yan HQ, Mao S, Russo R, Johnson J, Saykally R, Morris N, Pham J, He R, Choi H (2002) Controlled growth of ZnO nanowires and their optical properties. Adv Funct Mater 12:313–323
Ye JD, Gu SL, Zhu SM, Liu SM, Zheng YD, Zhang R, Shi Y (2005) Fermi-level band filling and band-gap renormalization in Ga-doped ZnO. Appl Phys Lett 86:192111–192114
Yuan G, Zhang W, Jie J, Fan X, Tang J, Shafiq I, Ye Z, Lee C, Lee S (2008) Tunable n-type conductivity and transport properties of Ga-doped ZnO nanowire arrays. Adv Mater 20:168–173
Zhong M, Li Y, Yamada I, Delaunay J–J (2012) ZnO-ZnGa2O4 core-shell nanowire array for stable photoelectrochemical water splitting. Nanoscale 4:1509–1514
Acknowledgements
This study was supported through the JSPS program, “Japan Society for the Promotion of Science”, Global COE Program, “Global Center of Excellence for Mechanical Systems Innovation,” and Grants-in-Aid for Scientific Research (B) 22360056 from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The authors thank Prof. Kazunari Domen and Prof. Jun Kubota (Department of Chemical System Engineering, The University of Tokyo) for the UV–VIS diffuse reflectance spectra measurements.
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SM-1) Graphs showing [F(R)*hv]1/2 versus hv calculated from the UV–VIS diffuse reflectance spectra
SM-2) Cathodoluminescence properties of the vertically aligned ZnO nanowires and the ZnO-ZGO core–shell nanowires
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Zhong, M., Li, Y., Tokizono, T. et al. Vertically aligned ZnO–ZnGa2O4 core–shell nanowires: from synthesis to optical properties. J Nanopart Res 14, 804 (2012). https://doi.org/10.1007/s11051-012-0804-x
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DOI: https://doi.org/10.1007/s11051-012-0804-x