Resistive switching characteristics of ZnO nanowires.

Binary transition metal oxides such as ZnO, TiO2, and MnO; and their various structures such as thin film, nanowire, and nanoparticle assembly; have been widely investigated for use in insulators in resistive random access memory (ReRAM), considered a next-generation nonvolatile memory device. Among the various driving mechanisms of resistive switching in insulating materials, the conductive filament model is one of the most widely accepted. Studies on spatially confined structures such as one-dimensional nanostructures and zero-dimensional nanoparticles to reveal the detailed filament constructing mechanism are warranted because low-dimensional nanostructures can provide more localized properties with a narrow dispersion of operational parameter values compared with thin-film structures. We investigated the resistive switching characteristics of ZnO nanowire (NW) structures. The NWs were grown on an Au/Ti/SiO2/Si substrate via the hydrothermal method. The empty space between the top and bottom electrodes was filled with a photoresist to prevent direct connection between the electrodes. The top electrode (Cr) and bottom electrode (Au), both with a thickness of -100 nm, were deposited by DC sputtering. The current-voltage (I-V) measurements were performed using a semiconductor characterization system. Additionally, the local current image and the point I-V characteristics for each NW were examined by replacing the top electrode with a conducting atomic force microscope tip. The Au-ZnO NW-Cr devices exhibited bipolar resistive switching behavior.