Electric Field Manipulation of Defects and Schottky Barrier Control inside ZnO Nanowires.

We directly measure the three-dimensional movement of intrinsic point defects driven by applied electric fields inside ZnO nano- and micro-wire metal-semiconductor-metal device structures. Using depth- and spatially resolved cathodoluminescence spectroscopy (CLS) in situ to map the spatial distributions of local defect densities with increasing applied bias, we drive the reversible conversion of metal-ZnO contacts from rectifying to Ohmic and back. These results demonstrate how defect movements systematically determine Ohmic and Schottky barriers to ZnO nano- and microwires and how they can account for the widely reported instability in nanowire transport.