Eur. Phys. J. B 60, 319-324 (2007)
https://doi.org/10.1140/epjb/e2007-00348-3

Variable-range hopping in Fe₇₀Pt₃₀ catalyzed multi-walled carbon nanotubes film

¹ Department of Physics, Jamia Millia Islamia, New Delhi, 110025, India
² Department of Electronic Science, University of Delhi South Campus, New Delhi, 110021, India
³ Department of Materials Science and Engineering & Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
⁴ Department of Applied Sciences & Humanities, Jamia Millia Islamia (Central University), New Delhi, 110025, India

Corresponding author: ^a mush_reslab@rediffmail.com

Received: 25 January 2007
Revised: 30 May 2007
Published online: 22 December 2007

Abstract

Using low-pressure chemical vapour deposition (LPCVD), multi-walled carbon nanotubes (MWNTs) are grown on nanocrystalline Fe₇₀Pt₃₀ film. The Fe₇₀Pt₃₀ nanocrystalline film is deposited by vapour condensation technique. The size of the nanoparticles varies from 5–10 nm, as inferred from SEM micrographs of Fe₇₀Pt₃₀ film. SEM and TEM observations of as-grown CNTs film reveal that these are multi-walled and their diameter varies from 30–80 nm and length is of the order of several micrometers respectively. There is a structural change from ordinary geometry of CNTs to bamboo shaped as suggested by TEM image. Raman spectra shows sharp G and D bands with a higher intensity of G band showing the presence of graphitic nature of the nanotubes. An experimental study of the temperature dependence of electrical conductivity of MWNTs film is done over a wide temperature range from (293–4 K). The measured data gives a good fit to variable-range hopping (VRH) and the results are interpreted using Mott's (VRH) model. The conduction mechanism of the MWNTs film shows a crossover from the exp[ -(T_o/T)^1/4] law in the temperature range (293–110 K) to exp[ -(T_m/T)^1/3] in the low temperature range (110–4 K). This behaviour is attributed to temperature-induced transition from three-dimension (3D) to two-dimension (2D) VRH. Various Mott's parameters like characteristic temperature (T_m), density of states at Fermi level N(E_F), localization length (ξ), hopping distance (R), hopping energy (W) have also been calculated using above-mentioned model.