Ni nanoparticle catalyzed growth of MWCNTs on Cu NPs @ a-C:H substrate T. Ghodselahi, S. Solaymani, M. Akbarzadeh Pasha and M.A. Vesaghi Eur. Phys. J. D, 66 11 (2012) 299 Published online: 04 December 2012 DOI: 10.1140/epjd/e2012-30074-8