Improvement of On/Off Ratio in Solution-Processed Graphene-Zinc Oxide Resistive Switching Memory by Blending with Polystyrene

Resistive switching (RS) memory devices are fabricated using solution processed graphene-zinc oxide (G-ZnO) and polystyrene (PS). G-ZnO is synthesized through solution processing at a low temperature. G-ZnO or G-ZnO:PS blended solution in a ratio of 1:5 by weight is spin-coated as the RS layer, and aluminum (Al) is adopted as the top and bottom electrode. Through UV-visible absorption, scanning electron microscopy (SEM), energy dispersive diffraction, and X-ray diffraction (XRD) analysis, G-ZnO and G-ZnO:PS films are confirmed as well-blended thin films. In the RS operation, the on/off ratio of low resistive state (LRS) and high resistive state (HRS) of G-ZnO device is approximately 10(4), which is increases to 10(8) in G-ZnO:PS device. PS, the insulating polymer, helps to improve the on/off ratio by reducing the off current in HRS. By analyzing the I-V curves in the HRS of G-ZnO device, the conduction mechanism is changed from ohmic conduction to space charge limited current (SCLC) in G-ZnO, while G-ZnO:PS shows the formation of a conductive path in insulators.