Charge Transport in Interpenetrating Networks of Semiconducting and Metallic Carbon Nanotubes

Carbon nanotube network field effect transistors (CNTN-FETs) are promising candidates for low cost macroelectronics. We investigate the microscopic transport in these devices using electric force microscopy and simulations. We find that in many CNTN-FETs the voltage drops abruptly at a point in the channel where the current is constricted to just one tube. We also model the effect of varying the semiconducting/ metallic tube ratio. The effect of Schottky barriers on both conductance within semiconducting tubes and conductance between semiconducting and metallic tubes results in three possible types of CNTN-FETs with fundamentally different gating mechanisms. We describe this with an electronic phase diagram. Carbon nanotubes are increasingly being used in the form of random network films for electronic applications. Thin (submonolayer) CNT films have been demonstrated as a material for low cost flexible transparent field effect transis-tors (FETs),1-7 as well as for gas, pH, chemical, DNA, and optical/IR sensors.8-11 The best CNTN-FETs to date have reached high ON/OFF ratios around 105 while at the same time achieving field effect mobilities on the order of 10 cm2