  Semiconductor nanowires are the building blocks of many nanoscale electrical
and neuromorphic circuits. Here, we demonstrate a simple arrangement wherein an
ethanol-adsorbed ZnO single nanowire, deposited between gold electrodes using
dielectrophoresis exhibits significant change in resistance when activated by
visible light. Here we have observed that the transition timescale between two
stable ohmic states, one in the dark and the other in the illuminated regime in
a single nanowire can occur in the submillisecond order, which is 7 orders of
magnitude lower than our previously reported switching timescale in bulk ZnO
thin films. A mathematical model of the light activated resistance switching
mechanism is proposed based on the adsorption-desorption kinetics of oxygen
molecules at the surface of the nanowires.
