Effect of fluorination on electrical properties of single walled carbon nanotubes and C60 peapods in networks

We present a comparative study of fluorinated single wall carbon nanotubes and C-60 peapods. The fluorination was carried out by xenon difluoride treatment at moderate temperature (100 degrees C). The fluorination level was determined by EDX. In empty nanotubes a fluorination level of 0.8 at.% was obtained, whereas the same treatment leads to 18 at.% in peapods (corresponding to a gross stoichiometry of C4F). TEM images show that this fluorination procedure does not affect the peapod structure. The elemental mapping carried out by EELS reveals homogenous distribution of fluorine along the carbon nanotube bundle. This chemical treatment is found to change the electrical properties of carbon nanotubes in bucky papers. Four-probe measurements indicate a conductivity decrease by up to two orders of magnitude at room temperature. The temperature dependence of the conductivity indicates a significant change in the charge carrier density of this system. Moreover, a non-linear behavior of the I-V characteristic is observed below 50 K in fluorinated peapods. (c) 2005 Elsevier B.V. All rights reserved.