Synthesis and characterization of 3C–SiC nanowires G. Attolini * , F. Rossi, M. Bosi, B.E. Watts, G. Salviati IMEM-CNR Institute, viale Usberti 37/A, 43100 Parma, Italy article info Article history: Available online 22 October 2008 PACS: 61.46.km 68.37.d 61.72.Nn Keywords: Silicon carbide Nanowires Planar defects abstract Silicon carbide nanowires have been synthesized by carbothermal reduction, from carbon monoxide and single crystal silicon. Transmission electron microscopy and cathodoluminescence studies confirm the growth of a cubic b-SiC core, coated with an amorphous oxide shell. Planar defects, as stacking faults and rotational twins, are present on (1 1 1) planes. The formation of short thick rods or long thin wires, depending on the growth temperature and time, is discussed. Ó 2008 Elsevier B.V. All rights reserved. 1. Introduction Recently, many studies have reported the preparation and char- acterization of 1D nanostructures such as nanowires (NWs) of oxi- des, nitrides, carbides, III–V’s, metals and silicon [1]. NWs often present chemical, physical, electrical, optical, and mechanical properties better than the bulk material, opening up new fields of fundamental research and nano-technological applications [2]. Cubic silicon carbide (b-SiC) is a wide band-gap semiconductor, which displays elevated hardness, electron mobility, thermal con- ductivity and resistance to chemical attack [3]. Hence, b-SiC NWs are interesting because their good physical and chemical proper- ties make them a promising material for devices operating in harsh environment [4]. Functionalized NWs have the potential to act as highly sensitive biochemical detector elements [5]. Many methods are being used to prepare SiC NWs, on silicon substrates, using a catalyst: chemical vapor deposition [6], vacuum evaporation of SiC [7], direct synthesis from Si and C powders [8]. In this article we report on the properties of b-SiC NWs, pre- pared by a reaction between single crystalline Si and CO using Ni catalyst. The synthesis is based on the carbothermal reduction of silica present as the native oxide on the surface of Si. The structural properties of the NWs investigated by scanning and transmission electron microscopies are discussed. 2. Experimental The growth of SiC NWs on (1 0 0) Si substrates was performed in an open-tube under a flow of CO and with N 2 or Ar as carrier gases, at temperatures between 1050 and 1100 °C. The substrate was cleaned with organic solvents in an ultra- sonic bath, dipped in a 0.01 M solution of nickel nitrate in ethanol and dried in an oven at 60 °C. The native silicon dioxide present on the substrate surface was not removed before treatment with the nickel–salt solution. The sample was placed in an open-ended tube, previously purged to remove air, which in turn was put inside a horizontal furnace. After the desired temperature profile was obtained, the tube was moved to position the substrate at the center of the fur- nace. When the temperature had stabilized the carbon monoxide was introduced into the tube and the growth proceeded for 15 and 90 min. At the growth temperature, carbon transport takes place in three stages: (i) CO adsorption on the silicon dioxide, (ii) diffusion through the SiO 2 and (iii) reaction with the silicon [9,10]. We can suppose that the reaction at the interface SiO 2 /Si is the following: 4ðCOÞ g þ 6Si ¼ 4ðSiCÞ s þ 2ðSiO 2 Þ s ð1Þ The morphology and density of the NWs were examined by Scanning Electron Microscopy (SEM). The crystalline structure was investigated by powder X-ray diffraction (XRD) and by con- ventional transmission electron microscopy (TEM) at 200 kV. The optical emission was studied by SEM-Cathodoluminescence (CL). 0022-3093/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2008.05.064 * Corresponding author. Tel./fax: +39 0521269267. E-mail address: giovanni@imem.cnr.it (G. Attolini). Journal of Non-Crystalline Solids 354 (2008) 5227–5229 Contents lists available at ScienceDirect Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/locate/jnoncrysol