Nanotech 2010

Is Aluminum Suitable Buffer Layer for Growth of Carbon Nanowalls?

P. Alizadeh Eslami, M. Ghoranneviss, S. Nasiri Laheghi
Islamic Azad University, IR

Keywords: carbon nanowalls


Self-assembled carbon nanostructures like carbon nanotubes (CNTs) and carbon nanowalls (CNWs) have attracted much attention for several applications, such as gas storage, membranes for electrochemical energy storage, and field emitters. Recently, Wu et al. [1] have reported the fabrication of CNWs standing vertically on a catalyzed substrate using microwave plasmaenhanced chemical vapor deposition (PECVD). In the other report, Wang et al. [2] have reported the synthesis of free-standing graphite sheets using an inductively coupled RF-PECVD employing CH4/H2 mixture. Very recently, Alizadeh et al. [3] and ghoranneviss et al. [4] have reported the growth of CNWs on a Fe catalyzed substrate using thermal chemical vapor deposition (TCVD) in atmospheric pressure. This work concentrates on the growth of CNWs on Fe nanocatalysts coated on Al as buffer layer by TCVD. Glass was used as a substrate. Effective parameters on the growth of the CNWs such as hydrocarbon gas flow ratio, deposition time, and temperature are investigated. The glass substrate is coated with Al thin film as a buffer layer in first step, and then Fe nanocatalyst coated on the Al buffer layer in second step. Carbon nanostructures are grown on the substrates by TCVD, using acetylene (C2H2) as carbon sources, and diluting the gases such as hydrogen (H2) and ammonia (NH3). Surface morphology of the substrate is observed by atomic force microscopy (AFM). Samples are characterized by scanning electron microscopy (SEM) and Raman spectroscopy. CNWs were obtained by the TCVD by applying C2H2/NH3/H2 mixture (20:80:100 sccm) for 45 minutes at atmospheric pressure, and at 600°C. Finally the CNWs growth was reproduced by the TCVD system at three different new conditions of a) 60 minutes, b) 700°C, and c) 48 sccm for hydrocarbon gas flow rate. Fig. 1 shows the SEM images of these CNWs. Results show forming some of maze like carbon nanostructures TCVD employing C2H2/NH3/H2 (20:80:100 sccm) for 45 minutes at atmospheric pressure, and 600°C substrate temperature. The results show that the increase of the deposition time from 45 to 60 minutes causes to producing no uniform carbon nanostructures on the surface, and increase of the C2H2 flow rate renders similar results too. Fig. 1 (d) shows the SEM image of the CNTs and CNWs obtained on the substrate by the TCVD employing C2H2/NH3/H2 (20:80:100 sccm) mixture for 45 minutes at atmospheric pressure and 700°C temperature.
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