Electrical Transport Through Single Wall Carbon Nanotubes

Zhen Yao1, Cees Dekker1, and Phaedon Avouris2

1 Department of Applied Physics, Delft University of Technology Lorentzweg 1, 2628 CJ Delft, The Netherlands [email protected] [email protected]

2 IBM Watson Research Laboratory Yorktown Heights, NY 10598, USA [email protected]

Abstract. We present a brief review of the phenomenal progress in electrical transport measurements in individual and ropes of single-wall carbon nanotubes in the past few years. Nanotubes have been made into single-electron transistors, field-effect transistors, and rectifying diodes. A number of interesting mesoscopic transport phenomena have been observed. More significantly, nanotubes exhibit strong electron-electron correlation effects, or so-called Luttinger liquid behavior, associated with their one-dimensional nature.

Electrical transport through Single-Wall Carbon Nanotubes (SWNTs) has generated considerable interest in the past few years (for earlier reviews, see [1,2]). This has been largely stimulated by many proposed applications of SWNTs in future nanoscale electronic devices based on their unique electronic properties and nanometer sizes. From the fundamental physics point of view, SWNTs provide a nearly perfect model system for one-dimensional (1D) conductors, in which electron-electron correlations have a profound influence on the properties of conduction electrons. They offer several clear advantages over other 1D systems. For example, comparing with semiconductor quantum wires, SWNTs are atomically uniform and well-defined; the strong confinement around the circumference leads to a large spacing between 1D subbands (~1 eV for a nm tube in contrast to ~10meV for typical semiconductor quantum wires), which means that the 1D nature is retained up to room temperature and well above. Comparing with other molecular wires, nanotubes are structurally robust and chemically inert. Moreover, because of the tubular structure, the Peierls distortion which normally makes other molecular wires semiconducting, becomes energetically unfavorable in carbon nanotubes - the lattice energy cost of rearranging the carbon atoms around the whole circumference is large while the gain in electronic energy is low since there are only two subbands at the Fermi energy.

Electrical characterization of individual SWNT molecules has been made possible by advances in both bottom-up chemical synthesis of the these materials and modern top-down lithographic techniques for making electrical

M. S. Dresselhaus, G. Dresselhaus, Ph. Avouris (Eds.): Carbon Nanotubes, Topics Appl. Phys. 80, 147-171 (2001) © Springer-Verlag Berlin Heidelberg 2001

contacts. The real breakthrough came when Smalley's group at Rice University developed a laser ablation method to grow high quality SWNTs in bulk quantity [3]. Since then, transport measurements have been carried out by a number of research groups. We will limit our discussion to results obtained on individual tubes or small individual ropes of SWNTs. The effect of doping as well as transport in multiwall nanotubes are described in other chapters of this book.

This paper is organized as follows. In Sect. 1, two of us (Z.Y. and C.D.) will describe transport measurements performed on isolated individual SWNTs. Semiconducting nanotubes can be distinguished from metallic ones from gate voltage dependence measurements at room temperature. At low temperatures, a number of interesting mesoscopic phenomena have been observed such as single-electron charging, resonant tunneling through discrete energy levels and proximity-induced superconductivity. At relatively high temperatures, tunneling conductance into the nanotubes displays a power-law suppression as a function of temperature and bias voltage, which is consistent with the physics of the 1D Luttinger liquid. Metallic nanotubes are able to carry a remarkably high current density and the main scattering mechanism for high energy electrons is due to optical or zone-boundary phonons. In addition, we will discuss devices for potential electronic applications such as junctions, rectifying diodes and electromechanical devices. In Sect. 2, one of us (Ph.A.) will discuss the importance of scattering and coherent-backscattering processes in the low-temperature transport in ropes and rings of SWNTs. Magneto-resistance measurements of coherence lengths, evidence for dephas-ing involving electron-electron interactions, zero-bias anomalies due to strong electron correlation, and carrier localization will be discussed. Finally, intertube transport within a rope will be addressed.

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