PERGAMON Carbon 39 (2001) 201–206 Curious aligned growth of carbon nanotubes under applied electric field a b a, * Anchal Srivastava , A.K. Srivastava , O.N. Srivastava a Department of Physics, Banaras Hindu University, Varanasi 221 005, India b Centre of Advance Technology, Indore, India Received 28 January 2000; accepted 6 April 2000 Abstract In the present investigation, we have investigated the effect of external voltage (field) on the alignment of graphitic nanotubes as a result of applied electric field. The details of alignment effect embodying variation of applied electric field corresponding to applied voltage between 2 to 10 volts, the variation of length and diameter of the tubes have been studied. It has been found that both the degree of alignment and optimum length ( |12 mm), diameter ( |60 nm) of the tubes are obtained for the applied electrical field corresponding to 6 volts. The applied electrical field for 6 volts has been estimated to 21 be ¯1889 volts cm . A feasible model for the effect of tube alignment due to the external electric field has been described and discussed.  2001 Published by Elsevier Science Ltd. Keywords: A. Carbon nanotubes; B. Arc discharge; C. Transmission electron microscopy (TEM), Scanning electron microscopy (SEM); D. Electrical properties 1. Introduction important step towards molecular electronics [13,14]. Carbon nanotubes are well suited for use as probe tip in Carbon nanotubes (CNTs) were first discovered by applications such as atomic force microscope [15]. Iijima through arc discharge method in helium ambient It has also been suggested that tubes might be used as [1,2]. These nanotubes have unique electronic and me- membrane material for batteries and fuel cells, anode for chanical properties [3,4]. Electronically, nanotubes are lithium ion batteries, capacitors and chemical filters [16]. expected to behave as ideal one-dimensional ‘‘quantum Many of these proposed applications will require special wires’’ [5] with either semiconducting or metallic be- synthesis routes so that the as grown tubes are aligned haviour, depending upon the diameter and orientation of forming tube bundles [17–22]. In order to verify the tube axis (parallel or perpendicular to the C–C bond) predicted curious properties, it is essential to develop [6–9]. One of the potential applications of carbon synthesis methods, which are capable of producing tubes nanotube is based on their unique mechanical properties. preferably in aligned / oriented configurations. Keeping In particular its high young’s modulus (average value is these aspects in view, the present studies were focussed on 1.8 T Pa) coupled with low density, nanotubes are ex- the high yield of oriented carbon nanotubes. pected to be the ultimate fiber [10]. Collins et al. reported Several feasible methods such as post synthesis quench an experimentally functioning carbon nano device (diode) and or annealing using large grain graphitic rod for plasma based on nanotube, having, a variety of structure cells evaporation etc., were applied for possible growth of [11,12]. Room temperature transistor based on a single oriented / aligned tubes. Seeking analogy from thin film carbon nanotube has been reported which marks an deposition, we attempted to explore the growth of tubes under applied electric field. Whereas our earlier study [23] on this was only exploratory emphasizing the observation *Corresponding author. Tel.: 191-542-317-468; fax: 191- of tube alignment, in the present study, we have described 542-361-937. E-mail address: ons@banaras.ernet.in (O.N. Srivastava). and discussed the details embodying the estimation of the 0008-6223 / 01 / $ – see front matter  2001 Published by Elsevier Science Ltd. PII: S0008-6223(00)00105-6