ABSTRACT
Attempts to make first CNT field effect transistors started in 19982. The filed has since exploded by theoretical and experimental researches that have looked into potential advantages and applications of such devices. There have thus been many publications in this field over the past few years. As suggested by these articles, single-walled carbon nanotube field-effect-transistors (SWNT-FETs) not only present a simple implementation for high performance nanoscale devices, but also are very attractive devices due their following outstanding electronic properties:
1) Ballistic transport Due to their one dimensional structure, backscattering of carriers is strongly suppressed in SWNTs. It leads to ballistic transport, meaning that the mean free path for charge carriers is longer than the channel length. In the literature3, carrier mobility as high as 8000 cm2V-1sec-1 is reported, which is already superior to the mobility of Si transistors with mobility values of 1400 cm2V-1sec-1. Ballistic transport of SWNT-FETs can yield very high speed transistors, necessary for high performance microprocessors and memory modules. 2) Flexible Device The strong covalent bonding of C-C affords the CNTs high mechanical and thermal stability. Furthermore, CNTs are transparent under visible light. Softness and transparency of CNTs can be utilized in thin film transistors for display devices. 3) Low power dissipation An IBM group has compared the electrical properties of SWNTFETs to both conventional high performance p-type Si-transistors and SOI MOSFETs5 as illustrated in Table 4.1. Important differences are in the off current Ioff, transconductance, and subthreshold swing. For VLSI circuits, the subthreshold swing S, defined by S = log[dVgs/d(log(Ids))], is a key parameter for a transistor to switch current. Clearly, a lower sub-threshold slope is more attractive since it is desirable to have the transistor “turn off” as close to the threshold voltage as possible. SWNT-FETs feature very low subthreshold slopes despite the fact that their fabrication
technology is still in infancy. Additionally, smaller off current Ioff in SWNT-FETs means lower static power dissipation.
