The electrical properties of carbon nanotube FETs (CNTFETs) have been studied in detail. The conduction type of the
CNTFETs was dependent on the work function of the contact metal, which suggests that Fermi level pinning at the
metal/nanotube interface is not strong. Based on the two-probe and four-probe resistance measurements, it has been
shown that the carrier transport at the contact is explained by the edge contact model even in the diffusive regime. The
chemical doping using F4TCNQ was effective in reducing not only the channel resistance but also the contact resistance.
In the CNTFETs fabricated using plasma-enhanced (PE) CVD-grown nanotubes, the drain current of the most of the
devices could be modulated by the gate voltage with small OFF current suggesting the preferential growth of the
nanotubes with semiconducting behavior.
Multichannel top-gate CNTFETs with horizontally-aligned nanotubes as channels have been successfully fabricated
using CNT growth on the ST-cut quartz substrate, arc-discharge plasma deposition of the catalyst metal, and ALD gate
insulator deposition. The devices show normally-on and n-type conduction property with a relatively-high ON current of
13 mA/mm. CNTFETs with nanotube network have also been fabricated by direct growth on the SiO2/Si substrate using
grid-inserted PECVD and using catalyst formed on the channel area of the FETs. The uniformity of the electrical
properties of the network channel CNTFETs were very good.
Finally, it has been shown that the surface potential profile measurement based on the electrostatic force detection in the
scanning probe microscopy was effective in studying the behavior of the CNTFETs such as the transient behavior and
the effect of the defects.
"Electrical properties of carbon nanotube FETs", Proc. SPIE 7037, Carbon Nanotubes and Associated Devices, 703703 (4 September 2008); doi: 10.1117/12.794695; https://doi.org/10.1117/12.794695