Carbon nanotubes are long meshed wires of carbon, the longest tubes are up to 1mm long and few nanometers thick.
Carbon Nanotube properties:
Size: 0.6-1.8 nm in diameter
Strength: 45 Billion Pascals
Resilience: Bent and straightened without damage
Conductivity: Estimated at 10exp9 A/cm2
Electrical Properties of CNT
Carbon nanotubes can be metallic or semiconductor type depending on their chirality. A chiral Vector C is defined as the vector from one open end of the tube to the other after it is rolled where, Vec.C = n vec.a1 + m vec.a2.
If (n-m) is divisible by 3, the tube is metallic and if (n-m) is not divisible by 3, the tube is semiconducting.
Carbon Nanotube FET
CNTs are strong flexible tubes that can be made conducting or semiconducting. CNT can be used as the conducting channel of a MOSFET. This new device is very similar to the CMOS FETs. All CNFETs are pFETs by nature.nFETs can be made through either annealing or doping. It has very low current and power consumption. Although tubes are 3nm thick CNFETs are still the size of the contacts, about 20 nm.
Challenges of Carbon Nanotube FET are: Multilevel interconnects not available, Chip density still limited to the density of contacts, Tube density not entirely exploited, Fabrication is still a stochastic process and alternatives to gold contacts need to be found.
There are several open problems and the initiatives have already been taken and suceeded on fabrication using DNA for self assembly, memory array of nanotubes using junctions as bit storages, using nanotube arrays to make computing elements and fabricate FPGAs using CNFETs and STM.