Physical Properties of Multiwall Nanotubes

Laszlo Forro1 and Christian Schonenberger2

1 Department of Physics, Ecole Polytechnique Fédérale de Lausanne 1015 Lausanne, Switzerland

[email protected]

2 Department of Physics and Astronomy, University of Basel 4056 Basel, Switzerland [email protected]

Abstract. After a short presentation on the preparation and structural properties of Multi-Wall carbon NanoTubes (MWNTs), their outstanding electronic, magnetic, mechanical and field emitting properties are reviewed. The manifestation of mesoscopic transport properties in MWNTs is illustrated through the Aharonov-Bohm effect, universal conductance fluctuations, the weak localization effect and its power-law temperature/field dependences. Measurements of the Young's modulus of individual nanotubes show the high strength of tubes having well-graphitized walls. Electron Spin Resonance (ESR) measurements indicate the low-dimensional character of the electronic states even for relatively large diameter tubes. The conducting nature of the tubes, together with their large curvature tip structure, make them excellent electron and light emitters suitable for applications.

With the discovery of Multi-Wall carbon NanoTubes (MWNTs) by Iijima in 1991, a new era has started in the physics and chemistry of carbon nano-structures [1]. After the synthesis of Single Wall carbon NanoTubes (SWNTs) in 1993 by Bethune and coworkers [2] and by Iijima et al. [3], the main stream of carbon research shifted towards the SWNTs, especially through the development of an efficient synthesis method for their large scale production by Smalley and colleagues [4]. Nevertheless, MWNTs present several complementary attractive features with respect to SWNTs, both for basic science and for applications. For example, one advantage of MWNTs is that they can be grown without magnetic catalytic particles, which are certainly disturbing for magnetic, and probably for transport measurements, as well. The larger diameter of the MWNTs enables us to study quantum interference phenomena, such as the Aharonov-Bohm effect, in magnetic fields accessible in the laboratory, while study of the same phenomenon would require 600 T fields in the case of SWNTs. The Russian-doll structure allows better mechanical stability and higher rigidity for the MWNTs which is needed for scanning probe tip applications. Even for making nanotube composites, for which the first step is the chemical functionalization of the tube walls, the multi-wall configuration is more advantageous, since efficient load transfer can be achieved without damaging the stiffness of the internal tubes.

The paper is organized as follows. First we will briefly review the production methods for MWNTs. Since the control of sample quality is a condition

M. S. Dresselhaus, G. Dresselhaus, Ph. Avouris (Eds.): Carbon Nanotubes, Topics Appl. Phys. 80, 329-391 (2001) © Springer-Verlag Berlin Heidelberg 2001

sine qua non for all studies, we present the purification and the structural characterization of the nanotubes. Different methods for filling the hollow interior of the nanotubes with a variety of elements is described. The longest section of the chapter is devoted to the transport properties of MWNTs, since these properties are really spectacular, and most of the mesoscopic transport phenomena can be studied on this system. The magnetic properties are investigated with the Electron Spin Resonance (ESR) technique and the fingerprints of low-dimensionality are shown. The field emission properties of MWNTs, which allowed the first application of these structures in flat panel displays, are studied for individual nanotubes. Light emission follows the discussion on electron emission. This phenomenon is presented not only in the field emission configuration, but also by using an STM tip for electron injection. The mechanical properties of MWNTs (as compared to SWNT ropes) are also discussed. A review of the role of the defects, deformations, and mechanical manipulation of MWNTs is also presented.

0 0

Post a comment