Local Surface Potential Measurements of Carbon Nanotube FETs by Kelvin Probe Force Microscopy

We fabricated carbon nanotube FETs (CN-FETs) by dielectrophoresis method. Two types of CN-FETs with either Au or Ti electrodes were prepared for the study of electrical junctions between metal electrodes and nanotubes. Local surface potential of the CN-FETs in working condition was mapped by Kelvin probe force microscopy (KFM). A large surface potential drop occurred at the interface between the Ti electrodes and the bundle of SWNTs, and this potential drop was changed by the applied gate voltage. This result suggests that the Schottky barrier at the drain edge is modulated by the gate bias.