Vertically aligned In2O3 nanowires are grown on InAs substrates by an electric field in the plasma sheath. The In2O3 nanowires are single crystalline with diameters less than 10 nm. Field emission results show that the aligned In2O3 nanowires have lower turn-on and threshold electric fields than nonaligned ones. This is discussed in terms of orientation, emitter shapes, and density of the In2O3 nanowires. (C) 2005 American Institute of Physics.