Carbon Nanotube Field Effect
Transistors
CNTs are graphene nano thickness
sheets rolled into tubes, considered as the fourth allotropic form of
carbon, along with the original three, coal, graphite and diamond. They
have unique electrical, mechanical, semiconducting properties and exist
in two forms; single wall (SW) and wall in a wall structure, called as
multiwall (MW), as shown in Figure 1 [19-21]. Sumio Iijima of Japan
discovered multiwall (MW) CNT in 1991, followed by single wall CNT in
1993 along with Donald Bethune (independently) [19]. CNTs show both
metallic and semiconducting properties (depending on their chirality or
chirality vector), have length in few micrometer and diameter ranging
from <1 nm to 50 nm. They are the best thermal conductors
(better than diamond), have tensile strength 102 ×
more than that of steel, can have a current density of
103 × than Cu (109A/cm2). CNT based field effect transistor (CNTFET) is
an important application of CNTs and the first CNTFET is fabricated by
S. J. Trans et. al. [21], as shown in Figure 1. Because of the
presence of CNT based channel in a CNTFET, it has a capability to
outshine conventional MOSFET in future. The CV/I characteristics of a
CNTFET is ~13× higher than that of a conventional
n-MOSFET [20-25].