Contact resistance modulation in carbon nanotube devices investigated by four-probe experiments

The contact resistance (R-cont) between nanotube and metal electrodes was directly measured in a four-terminal configuration of field-effect transistors for individual single-walled carbon nanotube (SWNT) bundles and a multiwalled carbon nanotube (MWNT). Both R-cont and the nanotube resistance (R-NT) in a semiconducting SWNT device drastically changed with gate voltage, while R-cont, being more than one-order smaller than R-cont in metallic SWNTs and MWNTs, was almost constant against the gate voltage. Carriers introduced either by gate voltage or chemical doping induced a rapid decrease in R-cont compared with the resistance of semiconducting SWNTs. (c) 2006 American Institute of Physics.