In a recent work (Nanotechnology 18, 095202), an ultimate scaling in the width of a gate electrode is demonstrated by a CNTFET with another CNT (diameter ∼3 nm) as a gate electrode. It is shown that such a short gate width is enough to turn the CNTFET on and off, and full channel operation is possible, independent of properties of the CNT–metal contacts. The device characteristics, such as transconductance and subthreshold swing, show an order of magnitude improvement with a CNT gate compared to the global back gate. A CNTFET with an ultra-short gate width is expected to have marked advantages in terms of operational frequency and will be a subject of future studies.
In realizing the CNTFET reported in the paper manipulations by an atomic force microscope were used, which would not be suitable for production purposes. But it is nonetheless useful for the proof-of-concept purpose and can be used to make prototype devices which cannot easily be fabricated with conventional lithography tools.