Charge storage in carbon nanotube field-effect transistors

Very significant hysteresis characteristics are found in single wall carbon nanotubes field-effect transistors (CNTFET) fabricated using AC dielectrophoresis method. The CNTFETs show ambipolar characteristics. Two clear hysteresis loops are observed when the gate voltage is forward and backward swept. The hysteresis characteristics are studied from room temperature down to 16 K. It is found that the hysteresis loops become smaller as temperature is decreased. We suggested that the hysteresis is caused by charge trapping in foreign species covering the single wall carbon nanotube. It is more difficult for charges to transfer into and out of the trapping center at a lower temperature; as a result, the hysteresis loops become much smaller at low temperature.