Abstract Submitted to the NANOTUBE'02 Workshop:

The unique electrical properties of carbon nanotubes make them promising candidates for a future nanoelectronics technology. Among the different nanotube-based devices demonstrated today the most useful for logic applications are the field-effect transistors (CNTFETs). I will review our efforts to evaluate the potential of these devices and compare it with that of silicon MOSFETs. The characteristics and optimization of p-type CNTFETs will be discussed first. I will then discuss the production of n-type and ambipolar CNTFETs. These can be produced not only by doping, but also by a simple vacuum annealing which removes adsorbed oxygen. The p to n transformation is reversible by re-exposure to oxygen. By comparing the characteristics of the two approaches we conclude that the effect of oxygen does not arise from bulk doping, but involves the modification of the Schottky barrier at the metal lead/ nanotube junction. Studies of the sub-threshold and saturation characteristics of the CNTFETs indeed show that the switching mechanism of the transistor does not involve the bulk of the nanotube, but is dominated by the modification of the Schottky barrier at the source region. In this sense, CNTFETs and Si MOSFETs operate differently and follow different scaling laws. Theoretical modeling illuminating these issues will be presented. Using the p-type and n-type CNTFETs we are able to fabricate the first nanotube ICs, complementary logic gates. Two types of NOT gates are presented: an inter-molecular and an intra-molecular gate.