Electric Transport Properties and Percolation in Carbon Nanotubes / PMMA Composites
- PDF / 275,503 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 56 Downloads / 251 Views
Electric transport properties and percolation in carbon nanotubes / PMMA composites
Jean-Michel Benoit, Benoit Corraze, Serge Lefrant, Patrick Bernier*, Olivier Chauvet Institut des Materiaux Jean Rouxel, Nantes University, 2 rue de la Houssiniere, BP 32229, Nantes, France * GDPC, Montpellier University, BP 26, 34095 Montpellier Cedex 05, France ABSTRACT Carbon nanotubes (CNT) possess remarkable physical properties. However, because of their size, they are difficult to handle. Making composites with them gives an alternative way to handle these objects and to make use of their properties at a macroscopic scale. Here, we present a comparative study of the transport properties of PMMA / nanotubes composite films with both SWNTs and MWNTs. At room temperature, the conductivity of the composites follows a pure percolation behavior when increasing the nanotube content. The universal scaling law for random site percolation with a very low percolation threshold (0.3 weight %) is obeyed over two orders of magnitude in CNT content. At low temperature, SWNTs and MWNTs based composites behave differently. While MWNTs composites still obey the percolation law, deviations are observed for SWNTs. The transport properties are discussed in terms of tube-tube contact and charging energy of the tubes.
INTRODUCTION Because of the way they are built and of their size, the carbon nanotubes are ideal quantum 1D systems. Most of the characteristic transport properties expected for quantum 1D conductors i.e. ballistic transport, Coulomb blockade, quantum box effects... [1-4] have already been probed at the nanometric scale. Such experiments are difficult to realize. They require the deposition of nano-electrodes, to treat the tubes in order to isolate them and to manipulate them. All these steps may affect the physical properties of the nanotubes because of chemical or physical modifications of the tube structure. However, experiments on untreated isolated tubes are not easy to perform. In this work, we propose to investigate the transport properties of insulating polymer/nanotubes composite films. When mixing conducting fillers in an insulating matrix, one expects to observe a percolation behavior. Close to the percolation threshold, the conductive pathway is controlled by a very small number of fillers. Our goal is to use this idea to probe if the intrinsic properties of untreated isolated nanotubes are accessible by experiments at a macroscopic scale. We show that the transport properties of PMMA/SWNTs and PMMA/MWNTs composite thin films indeed obey the percolation theory. The investigations of the transport mechanism of these composite thin films suggest that some of the intrinsic properties of the nanotubes can be deduced from experiments at a macroscopic scale.
Z3.28.1
EXPERIMENTAL SWNTs and MWNTs are produced by the arc discharge method in GDPC Montpellier and TCD Dublin respectively. The typical purity of the SWNTs mat and of the MWNTs mat is close to 70 wgt % and 50 wgt % respectively. Composite films are obtained by dispersi
Data Loading...
