Growth of vertically aligned carbon nanotubes on silicon and quartz substrate by spray pyrolysis of a natural precursor: Turpentine oil Rakesh A. Afre a, * , T. Soga a , T. Jimbo a , Mukul Kumar b , Y. Ando b , M. Sharon c a Department of Environmental Technology and Urban Planning, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-855, Japan b Department of Material Science and Engineering, Meijo University, Tempaku-ku, Nagoya 468-8502, Japan c Nanotechnology Research Laboratory, Birla College, Kalyan 421-304, India Received 10 May 2005; in final form 8 August 2005 Available online 30 August 2005 Abstract Vertically aligned carbon nanotubes (VACNTs) were grown by spray pyrolysis of turpentine oil and ferrocene mixture at 700 °C. Using this simple method, we report the successful growth of vertically aligned nanotubes of 300 lm length and diameter in the range of 50–100 nm on Si(1 0 0) substrate. The ferrocene act as an in situ Fe catalyst precursor and forming the nanosize iron par- ticles for formation of VACNTs on Si and quartz substrates. Morphological differences between aligned carbon nanotubes grown on different substrates are studied and discussed by SEM, TEM and Raman spectroscopy characterizations. Ó 2005 Elsevier B.V. All rights reserved. 1. Introduction Carbon nanotubes (CNTs) have been studied exten- sively since they were discovered in 1991 [1] and have opened a new science and technology on nanoscale materials. Carbon nanotubes have outstanding elec- tronic, thermal and mechanical properties [2]. Because of these properties, CNTs are interesting material for applications in nanoelectronics or as reinforcing agents in composite materials. Arrays of aligned nanotubes (ANTs) represent an interesting modification of nano- tubes, where the quasi-one dimensional carbon cylinders are oriented in a parallel fashion perpendicular to the substrate. Due to the excellent field emission properties of CNTs, ANTs might find application in flat panel dis- plays [3]. It has also been proposed to use ANTs as highly efficient media for high harmonic generation [4]. For such applications large arrays of ANTs are neces- sary. Earlier ANTs were produced by drawing a suspen- sion of pre-produced nanotubes through a filter [5]. Several research groups have employed the catalytic pyrolysis with iron/silica nanoparticles–C 2 H 2 gas [6], ferrocene benzene mixture [7,8], ferrocene–xylene mix- ture [9,10], ferrocene C 2 H 2 mixture [11], and Fe(CO) 5 [12]. Kamalakaran et al. [13] have grown self-aligned nanotubes by a simple spray pyrolysis method but not on a substrate. For various applications ANTs are needed on specific substrates. Ren et al. [14] have used plasma-enhanced CVD method and synthesized well- aligned nanotubes from ethylene on Ni-coated glass substrate. However, apart from the expensive, cumber- some methods, all of these precursors are related to fos- sil fuels that are not regenerative. Recently, there have been appreciable attempts of CNT synthesis from regen- erative precursors such as camphor [15,16] and turpen- tine oil [17]. However, no aligned nanotubes could be produced from turpentine oil. Hence, the aim of the 0009-2614/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.cplett.2005.08.040 * Corresponding author. Fax: +81 52 735 7120. E-mail address: rakeshafre123@yahoo.co.in (R.A. Afre). www.elsevier.com/locate/cplett Chemical Physics Letters 414 (2005) 6–10