TABLE OF CONTENTS Since their discovery in the early 1990's [5.6, 5.7], single-walled carbon nanotubes (SWNT's) have been the subject of intense research. They display remarkable electronic, mechanical, and thermal properties [5.8] and are, therefore, promising for new device applications. Carbon nanotube (CNT) electronics is one such promising application [5.9]. Although the field is still new, field-effect transistors [5.1, 5.2, 5.3] and circuits [5.10, 5.11, 5.12], pn junctions [5.12], bio-sensors [5.13], and optical emitters [5.14] have all been demonstrated. Carbon nanotube electronics is both scientifically and technologically interesting.
This chapter is an introduction to carbon nanotube electronics; it is not a comprehensive look at the field. We will examine carbon nanotube field-effect transistors (CNTFETs) and use them as a specific example to see how the ideas developed in the previous section are applied to much different material systems. We begin by reviewing the basic electronic properties of CNTs, which include band structures and the density-of-states (DOS).
The bandstructure of a SWNT can be understood in terms of the bandstructure of graphene, a two-dimensional sheet of carbon atoms that is rolled up to form a nanotube. Graphite consists of layers of carbon atoms arranged in a hexagonal lattice like chicken wire. Each layer, known as graphene, consists of a two-dimensional sheet of carbon atoms in the honeycomb structure shown in Fig. 5.8a. The three nearest neighbor bonds for each carbon atom are made up of the carbon s orbital and two of the three p orbitals. The strong sp
