Analysis of operation mechanism of field effect transistor composed of network of high-quality single wall carbon nanotubes by scanning gate microscopy

Field effect transistors (FETs) whose channel is composed of a network of high-quality single wall carbon nanotubes (SWNTs) have been studied to investigate the mechanism of the device operation via scanning gate microscopy (SGM) at room temperature. SWNTs synthesized by CoMoCAT® process was used for the formation of the network. Clear SGM responses were observed only at some points but not uniformly in a whole of the channel. The observed responses correspond to positions where two SWNTs are crossing. Back gate voltage dependence of the SGM images and an electrostatic force microscopy image were also studied. One of the possible mechanisms of the SGM response is considered as a modulation of Schottky barrier formed at junctions between metallic and semiconducting SWNTs. Such junctions suggestively play an important role in the FET operation.