Emerging Nanoelectronic Devices

16Carbon Nanotube Electronics

Aaron D. Franklin

Department of Electrical and Computer Engineering and Department of Chemistry, Duke University, USA

16.1 Carbon Nanotubes – The Ideal Transistor Channel

What made silicon so attractive for use as the transistor industry's foremost semiconducting material was primarily its accessibility compared to semiconductors with more ideal attributes. Compared to germanium, on which the early field-effect transistors (FETs) were demonstrated, silicon had a less desirable indirect bandgap and much lower mobility for electrons and holes. However, silicon was (and is) abundant and had a native oxide, SiO₂, which proved viable as a gate dielectric and an excellent passivation layer for surface states. After over five decades of shrinking down the size of silicon metal-oxide-semiconductor FETs (MOSFETs), the scaling limit is now effectively reached and industry is clamoring for a more scalable and more ideal replacement. This chapter presents the single-walled carbon nanotube (CNT) as the ideal semiconducting material for yielding scalable, high-performance FETs for the next generation of electronics.

16.1.1 Electronic Structure of a CNT

Physically, a CNT is composed of a single cylindrical shell of carbon atoms that are sp²-bonded in a honeycomb lattice. It is instructive to consider the CNT as a sheet of graphene rolled into a seamless cylinder, providing both visual conception and insight into the electronic structure of a nanotube. Consider ...