chaPter 7 nanomaterials: Properties
236
transistors, are currently made of copper, but as electronic circuits
continue to shrink, copper interconnects will suffer from overheating. Conventional metal wires can typically exhibit current densities of 10
5 A/cm
2 until resistive heating becomes a problem. On
the other hand, because of the nearly one-dimensional electronic
structure of CNTs, electronic transport in metallic SWNTs occurs
ballistically along the nanotube length, allowing the conduction
of high currents with no heating. In fact, current densities up to
10
9 A/cm
2 have been observed in SWCNTs. This is because the
electronic states are confined in the directions perpendicular to
the tube axis. As a result, the remaining conduction path occurs
along the tube axis. Due to the lack of phonon and/or impurity
scattering perpendicular to the tube, CNTs behave as 1-D ballistic
conductors.
Field-effect transistors (FETs), a type of transistor used for weaksignal amplification, are currently made from silicon. However,
these devices are still a few hundred nanometers in size. The use
Figure 7.40
Chirality in nanotubes, describing the way in
which the graphite sheets are rolled up to form a
particular tube structure.
Armchair
Zig-zag
Chiral
236
transistors, are currently made of copper, but as electronic circuits
continue to shrink, copper interconnects will suffer from overheating. Conventional metal wires can typically exhibit current densities of 10
5 A/cm
2 until resistive heating becomes a problem. On
the other hand, because of the nearly one-dimensional electronic
structure of CNTs, electronic transport in metallic SWNTs occurs
ballistically along the nanotube length, allowing the conduction
of high currents with no heating. In fact, current densities up to
10
9 A/cm
2 have been observed in SWCNTs. This is because the
electronic states are confined in the directions perpendicular to
the tube axis. As a result, the remaining conduction path occurs
along the tube axis. Due to the lack of phonon and/or impurity
scattering perpendicular to the tube, CNTs behave as 1-D ballistic
conductors.
Field-effect transistors (FETs), a type of transistor used for weaksignal amplification, are currently made from silicon. However,
these devices are still a few hundred nanometers in size. The use
Figure 7.40
Chirality in nanotubes, describing the way in
which the graphite sheets are rolled up to form a
particular tube structure.
Armchair
Zig-zag
Chiral