Availableonlineatwww.sciencedirect.com SCIENCE DIRECT state ELSEVIER olid State Sciences 7(2005)45-51 Sciences Structure-directing If-organized. one-dimensional Zno single-crystal whiskers Hongwei Hou, Yi Xie*, Qing Li Structure Research Laboratory and Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026. PR China Received 8 January 2004; received in revised form 7 July 2004; accepted 11 October 2004 Available online 15 December 2004 Abstract One-dimensional (ID)Zno tubular and epitaxial whiskers were synthesized in a structure-directing agent(CTAB) under hydrothermal growth conditions, respectively. FE-SEM, SEM, TEM and SaEd observation reveals that the hexagonal open-ended Zno tubular are with diameters of 4 um and the length of up to 20 um, and zno epitaxial whiskers with diameters of 4 um and the length of 10 structure directing effect of CTAB, the pH value of the system and structure of wurtzite Zno play important roles in the growth of Znd crystalline whiskers @2004 Elsevier SAS. All rights reserved. Keywords: ZnO; Structure-directing: Single-crystal whiskers; Tubular; Epitaxial 1. Introduction whiskers were shaped via oxidation of the Zns powders at 1 100C [12] or formed by pyrolysis of zinc acetylaceto- Recently, many research efforts have been invested in nate at 500C[13]. And dendritic side-branch Zno whiskers the area of wide band-gap semiconductor materials due to on the edge of the hexagonal columnar structure were syn- their potential applications in short wavelength optical de- thesized using a chemical vapor deposition technique [14] vices [1]. ZnO is a ll-VI compound semiconductor with a However, to the best of our knowledge, no epitaxial ZnO wide and direct band gap of 3.3 eV and large exciton bind- single-crystal whiskers have been reported, and also lit ing energy (60 meV)[2]. From this aspect, Zno has been tle work has been done for the tubular ZnO single-crystal investigated as solar cells, gas sensors, a short-wavelength whiskers using mild, low cost and easy controllable metho light-emitting and laser diodes and piezoelectric material Here, for the first time, we report a simple hydrothermal syn- [3, 4]. Because of its rigidity, high aspect ratio and excellent thesis of one-dimensional(ID)tubular ZnO single-crystal chemical stability, ZnO crystal whiskers have been success- whiskers and epitaxial ZnO single-crystal whiskers using fully used as probing tip for atomic force microscopy and structure-directing agent cetyltrimethylammonium bromide scanning tunneling microscopy [5]and reinforced compos- ( CTAB), respectively. It is expected that the novel tubular e materials [6] whiskers may offer exciting opportunities for potential appli Up to now, evaporation growth method [6-8] and hy- cations in catalysis, microsized waveguides or optical fibers drothermal method [9], have been applied to grow ZnO pris- [15] and the novel epitaxial whiskers may offer exciting op- matic whiskers. Recently, polycrystalline tubular ZnO was portunities for homozygote in photoelectronic devices fabricated by a solvothermal route using ethanol as solvent [10] and synthesized by thermal evaporation of the Zn/zno powders at1300°C The single-crystalline tubular Zno 2. Experimental Corresponding author. The synthesis of Zno single-crystal whiskers was car- ried out as follows: Analytical pure zinc(If)acetate dihydrate 1293-2558/S-see front matter 2004 Elsevier SAS. All rights reserved dor: 10. 1016/j. solidstatesciences 2004 10.037Solid State Sciences 7 (2005) 45–51 www.elsevier.com/locate/ssscie Structure-directing self-organized, one-dimensional ZnO single-crystal whiskers Hongwei Hou, Yi Xie ∗ , Qing Li Structure Research Laboratory and Department of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, P.R. China Received 8 January 2004; received in revised form 7 July 2004; accepted 11 October 2004 Available online 15 December 2004 Abstract One-dimensional (1D) ZnO tubular and epitaxial whiskers were synthesized in a structure-directing agent (CTAB) under hydrothermal growth conditions, respectively. FE-SEM, SEM, TEM and SAED observation reveals that the hexagonal open-ended ZnO tubular whiskers are with diameters of 4 µm and the length of up to 20 µm, and ZnO epitaxial whiskers with diameters of 4 µm and the length of 10 µm. The structure directing effect of CTAB, the pH value of the system and structure of wurtzite ZnO play important roles in the growth of ZnO single crystalline whiskers.  2004 Elsevier SAS. All rights reserved. Keywords: ZnO; Structure-directing; Single-crystal whiskers; Tubular; Epitaxial 1. Introduction Recently, many research efforts have been invested in the area of wide band-gap semiconductor materials due to their potential applications in short wavelength optical de￾vices [1]. ZnO is a II–VI compound semiconductor with a wide and direct band gap of 3.3 eV and large exciton bind￾ing energy (60 meV) [2]. From this aspect, ZnO has been investigated as solar cells, gas sensors, a short-wavelength light-emitting and laser diodes and piezoelectric material [3,4]. Because of its rigidity, high aspect ratio and excellent chemical stability, ZnO crystal whiskers have been success￾fully used as probing tip for atomic force microscopy and scanning tunneling microscopy [5] and reinforced compos￾ite materials [6]. Up to now, evaporation growth method [6–8] and hy￾drothermal method [9], have been applied to grow ZnO pris￾matic whiskers. Recently, polycrystalline tubular ZnO was fabricated by a solvothermal route using ethanol as solvent [10] and synthesized by thermal evaporation of the Zn/ZnO powders at 1300 ◦C [11]. The single-crystalline tubular ZnO * Corresponding author. E-mail address: yxielab@ustc.edu.cn (Y. Xie). whiskers were shaped via oxidation of the ZnS powders at 1100 ◦C [12] or formed by pyrolysis of zinc acetylaceto￾nate at 500 ◦C [13]. And dendritic side-branch ZnO whiskers on the edge of the hexagonal columnar structure were syn￾thesized using a chemical vapor deposition technique [14]. However, to the best of our knowledge, no epitaxial ZnO single-crystal whiskers have been reported, and also lit￾tle work has been done for the tubular ZnO single-crystal whiskers using mild, low cost and easy controllable method. Here, for the first time, we report a simple hydrothermal syn￾thesis of one-dimensional (1D) tubular ZnO single-crystal whiskers and epitaxial ZnO single-crystal whiskers using structure-directing agent cetyltrimethylammonium bromide (CTAB), respectively. It is expected that the novel tubular whiskers may offer exciting opportunities for potential appli￾cations in catalysis, microsized waveguides or optical fibers [15] and the novel epitaxial whiskers may offer exciting op￾portunities for homozygote in photoelectronic devices. 2. Experimental The synthesis of ZnO single-crystal whiskers was car￾ried out as follows: Analytical pure zinc(II) acetate dihydrate 1293-2558/$ – see front matter  2004 Elsevier SAS. All rights reserved. doi:10.1016/j.solidstatesciences.2004.10.037