Electrical Transport in Polymer-Covered Silicon Nanowires

The influence of polymer layers wrapped around n-type Si nanowires (NW) on their electrical characteristics is investigated. The NWs are fabricated via metal induced excessive oxidation and dissolution of Si, and have a diameter of ~350 nm. Single wires are covered by various polymer layers. The polymers used are both insulating [poly (methyl methacrylate) (PMMA), polyethylene (PE), polystyrene, and polyethylene oxide (PEO)] and semiconducting poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate). Four-point probe measurements are used to measure the conductivity changes of single NWs. The NW resistivity increases with PE and PMMA coverage, but decreases with PEO coverage. The changes are attributed to carrier exchange between the polymer and NW. The measurements also confirm active electron trapping with PE coverage that is not observed with the other polymers.