Single-string carbon nanotube field effect transistors fabricated by two-step dielectrophoresis

Carbon nanotube field effect transistors (CNT FETs) with a long, single channel are an essential ingredient for gas and bio sensors, because a single spot modification of the channel can change the conductivity of the whole device. Herein, the two-step dielectrophoresis (DEP) technique was used to fabricate single string, single wall CNT FETs with a length longer than 10 μm. The single string FET showed an on/off ratio and transconductance which are larger than those of the network FET on the same substrate. The observed characteristics were explained by a circuit simulation. We also demonstrated that our method could be applied to flexible substrates.