2.1 Introduction

Metallic carbon nanotubes have attracted significant attention because their ability to carry high current densities is unparalleled in the family of emerging nanowires. Ballistic transport has been observed, and values for the conductance that approach the theoretical limit have been measured at small biases. They hold promise as interconnects in both nanoelectronics and molecular electronics because of their low resistance and outstanding mechanical properties (Fig. 2.1). A problem with interconnects in the semiconductor industry is breakdown of copper wires due to electromigration when current densities exceed 10 ⁶A/cm ². Preliminary work has shown that arrays of carbon nanotubes can be integrated with silicon technology and hold promise as vertical vias to carry more than an order of magnitude larger current densities than conventional ones [1,2], and reference [3] demonstrated that multiwall nanotubes carry current densities approaching 10 ⁹A/cm ². Single wall metallic nanotubes are also important from the perspective of molecular electronics, where they can be used either as interconnects or nanoscale contacts.

Figure 2.1: (a) Wiring in an integrated circuit. The horizontal interconnects are shown in yellow and the vertical interconnects are shown in gray. Figure from IBM Journal of Research and Development. (b) An example of a multiwall carbon nanotube array grown in a silicon oxide via, which can potentially be used as a vertical interconnect. Figure from Ref. [1]. (c) A pictorial representation of a single wall nanotube used as a vertical interconnect.

The unique band structure of metallic carbon nanotubes,...