Diameter-dependent internal gain in ZnO micro/nanowires under electron beam irradiation

Abstract

We observed a conductivity gain in intrinsic ZnO micro/nanowires at characteristic diameter scales from nanoscale to microscale by employing metal–semiconductor–metal structures with ohmic contacts under electron beam irradiation. The conductivity is enhanced under electron beam illumination and the magnitude is inversely proportional to the micro/nanowire diameter from 400 nm to 1300 nm at constant radiation intensity. We also introduced a model to simulate the diameter-dependent electric potential distribution. We attribute these observations to the variation of the effective electron carrier density upon varying diameters of ZnO micro/nanowires, as a result of field effects from the diameter-dependent population of the surface-trapped holes.