PECVD-growth of carbon nanotubes using a modified tip-plate configuration H. Hesamzadeh, B. Ganjipour, S. Mohajerzadeh a, * , A. Khodadadi b , Y. Mortazavi b , S. Kiani a Department of Electrical and Computer Engineering, University of Tehran, Tehran 14399, Iran b Department of Chemical Engineering, University of Tehran, Tehran 14399, Iran Available online 6 February 2004 Abstract We report a modified tip-plate configuration for the growth of carbon nanotubes using a plasma-enhanced chemical vapor deposition (PECVD) method. Tip-plate configuration allows operation at atmospheric pressures, which in turn simplifies the fabrication procedure. Using this method we have realized carbon nanotubes on SiO 2 -coated silicon substrates at temperatures ranging from 650 to 750 °C. Tube diameter varies with the growth temperature and ranges from 20 to 200 nm in different samples. Near vertical growth has been observed at lower temperatures using a mixture of 90% H 2 and 10% ethylene as the feed gas. Scanning electron microscopy (SEM) has been exploited to study the morphology of the grown layers. Nickel has been used as the growth catalyst, deposited with various thicknesses to study the nano-island formation and its effects on the growth of nanotubes. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: A. Carbon nanotubes; B. Catalyst, Heat treatment, PECVD 1. Introduction Carbon nanotubes (CNTs) have received consider- able attention since their first discovery in 1991 [1]. Be- cause of their potential applications in electronics devices [2], nano-technology tools [3,4] and novel nano- scale materials [5,6], many methods have been developed for the synthesis of CNTs, among which one can iden- tify arc-discharge [7], laser ablation [8] and high pressure chemical vapor deposition (CVD) [5,9–12]. Many applications desire growth of nanotubes with well- defined diameters and lengths. Multi-wall-nanotubes (MWNT) can be deposited onto silicon substrates coated with silicon dioxide using plasma-enhanced chemical vapor deposition (PECVD) methods provided a suitable transition metal has covered the surface of the substrate acting as the growth catalyst [13–18]. The essential parameters involved in the growth of carbon nanotubes are the type of the feed gas, the nature of catalyst as well as the substrate temperature during the growth. Acetylene is a frequently used gas for the growth of nanotubes at low temperatures, although methane is also used for the formation of single-wall tubes, which requires higher growth temperatures. Well-aligned na- notubes were first grown using a hot filament plasma enhanced CVD [14], subsequently various plasma methods have been developed to achieve vertical align- ment of the grown nanotubes [16–18]. One of the important problems in the production of CNTs is its cost and availability of sufficiently large quantities of CNTs. We have used of a modified PECVD method for the growth of carbon nanotubes at atmospheric pressures. This method is promising and the preliminary data observed from the growth of CNTs show possibility of vertical alignment of tubes at temperatures as low as 650 °C. Also operation at atmospheric or sub-atmo- spheric pressures facilitates the fabrication procedure, resulting in a low cost and high efficiency method for CNT production. A gas mixture composed of ethylene and hydrogen has been used as the source of growth and the presence of a direct current (DC) plasma be- tween a pointed tip and the opposite plate significantly enhances the growth at reduced temperatures. Thin layers of nickel were used as the catalyst layer and a pretreatment was needed to form islands as the seed of tube growth. * Corresponding author. Tel./fax: +98-21-801-1235. E-mail address: smohajer@sun1.vlsi.uwaterloo.ca (S. Mohajer- zadeh). 0008-6223/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbon.2003.12.017 Carbon 42 (2004) 1043–1047 www.elsevier.com/locate/carbon