Highly Ordered and Well-oriented Single-crystal CdTe Nanowire Arrays by Direct-current Electrodeposition
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D.P. Yu State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871, People’s Republic of China (Received 31 October 2001; accepted 15 April 2002)
Highly ordered CdTe nanowire arrays were prepared by electrochemical deposition into the pores of anodic aluminum oxide templates from an ethylene glycol bath containing CdCl2, TeCl4, and KI. Electron microscopy results showed that the length, diameter, and direction of growth of the nanowires were quite uniform. X-ray diffraction, transmission electron microscopy, and high-resolution electron microscopy investigations showed that these nanowires had a crystalline structure of hexagonal CdTe single crystal with a uniform [001] growth direction.
I. INTRODUCTION
Semiconductor nanowires have been attracting much attention in recent years for their potential applications in mesoscopic research and nanodevices.1–5 There are mainly three experimental approaches to fabricating semiconductor nanowires with uniform diameters. One method is laser ablation of metal containing semiconductor targets through a vapor-liquid-solid growth mechanism.6,7 A critical feature of this method is that the catalyst used to define one-dimensional growth and thus the metal always is observed at the nanowire end. The second method is oxide-assisted semiconductor nanowire growth by laser ablation, thermal evaporation, or chemical vapor deposition.8–11 In approach, each nanowire consists of an amorphous oxide shell, and a high density of defects has been observed in the crystalline semiconductor core.9 The third is a template synthesis method, the key components of which are template and electrodeposition.12–19 In this method, thin fibrils of the desired materials are electrochemically synthesized within the voids of the template material. Due to cylindrical pore geometry and monodisperse diameters, corresponding cylindrical and oriented nanostructural materials with a narrow diameter distribution are obtained. On the other hand, because the growth is controllable almost exclusively in the direction normal to the substrate surface, electrochemical synthesis in a template is taken as one of the most efficient methods in controlling the growth of nanowires. Although crystallized semiconductor
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Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 17, No. 7, Jul 2002
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nanowire arrays such as CdS, CdSe, Ag2Se, etc., have been fabricated using direct or alternating current electrodeposition processes,13–17 synthesis of aligned and well-distributed single-crystal semiconductor nanowires is still a challenging research area. Recently, CdS and TiO2 single-crystal nanowires have been obtained by electrochemically induced deposition.18,19 In this paper, we report our work on synthesis of aligned single-crystal CdTe nanowire arrays based on direct current (dc) electrolysis into the pores of an anodic aluminum oxide (AAO) template from an ethylene glycol bath containing CdC
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