Approaching the Frontier Between Fiber Devices and Single Molecule Devices in Redox Gated Junction

Abstract

Charge transport in two conducting polymer [poly(bithiophene) (PBT) and poly(ethylenedioxythiophene) (PEDOT)] nanojunctions was investigated using two microelectrodes, separated by micrometric gap. Such junctions are redox gated and exhibit conductance switching between low and high resistance states at potential of 1.2 and 0 V, respectively. Devices with conductance between 100 and 500 nS in the oxidized state were easily obtained, indicating control of the charge transport within the whole micrometric gap by a limited number of wires (less than 100 oligomeric strands). I/V characteristics and steady state conductance measurements, for various gate potential, indicate that measured on/off ratios can be as high as 1000 despite the small number of strands controlling the charge transport properties of the devices. Finally, we show that generating nanojunctions whose smallest diameter is below 4 nm on a length close to the size of a polaron, or its localization length, makes it possible to reach the frontier between fiber devices and single molecule devices.