Abstract:
Carbon nanotubes (CNT) are one of the most fascinating discoveries in 20th
century which exhibits superior properties in mechanical , electrical, optical and
thermal properties. CNT can be either semiconducting or metallic, based on its
chirality. Electronic industry uses CNT as an active element in the fabrication of
electrical circuit. CNT can also be used for spintronics applications. Spintronics has
emerged as a new field where electron spin is used as a carrier of information instead
of electron charge.
Fe filled CNT are usually synthesized by pyrolysis of ferrocene, however this
process is not known to yield good quality Ni and Co filled CNT. In the present work,
the synthesis of cobalt-filled multi - walled carbon nanotubes has been achieved by
the process of Chemical Vapor Deposition using pyrolysis of Cobaltocene. Here
cobaltocene along with camphor was used as a precursor. This combination yields
highly aligned forests of Co filled CNT with length of the forest upto a few 100
micro-meters. Synthesis of these filled tubes has been achieved by adjusting
experimental parameters like sublimation temperature, pyrolysis temperature, argon
flow rate and the amount of precursor. These samples have been characterized by
Raman, X-ray diffraction and Scanning Electron Microscopy. The Raman
spectroscopy shows well defined D and G bands with the Id/Ig ratio of 0.639 with the
occurrence of 2D band as well. Magnetic measurement shows that it exhibit
ferromagnetic behaviour with the coercive field of 660 Oe due the filling of cobalt
inside the nanotube shell. These filled CNTs forests have been drop-cast on a glass
substrate and preliminary electron transport measurements have also been reported
here.
The aligned forest of Co filled CNT have also been converted to Co oxides by
suitable annealing and the sample thus formed has been characterized by SEM, XRD
and Raman. These samples are relevant for battery material as well as for spintronic
applications.
