Formation and subsequent inclusion of fullerene-like nanoparticles in nanocomposite carbon thin films

The use of carbon nanotubes, fullerenes and fullerene-like cages in electronic applications is limited because of the practical difficulties in creating electrode contacts to them. This is because such carbon nanoparticles are produced in powder form or as aligned carbon nanotubes (individual or in bundles). The latter might soon be grown at pre-defined positions and across metal electrodes in electronic circuits but the process is anticipated to consist of several complex steps. The formation of carbon based thin films with embedded carbon nanoparticles is a versatile and attractive alternative which might enable researchers to capitalize on the electronic properties of carbon nanoparticles to produce novel electronic thin film materials. Here we present results on the formation mechanism of nanocomposite carbon thin films deposited using a carbon arc between two graphitic electrodes in a localised high N-2 gas pressure environment. The films were studied using high resolution electron microscopy (HREM) and electron energy loss spectroscopy (EELS). HREM images revealed that the films consist of two different phases: (i) a speckle type background and (ii) inclusions consisting of clusters of crystalline carbon nanoparticles. The presence of the N-2 gas pressure is found to be critical in determining the shape of the nanoparticles and the size of the clusters seen within the film. A possible process for the formation and the subsequent inclusion of the carbon nanoparticle clusters using an arc discharge is proposed based on the examination of films deposited using (i) differing N-2 gas pressures and (ii) carbon cathodes with different usage "histories". (C) 2004 Elsevier Ltd. All rights reserved.