▎ 摘　　要

A graphene sheet was used as one of the electrodes of a HfO2 metal-oxide-based resistive random access memory. We find dramatic differences in the device characteristics as voltages with opposite polarities are used to form the resistive memory devices. Using experimental measurements of the switching characteristics and the corresponding low and high resistance state, we compare the two different operating modes of a graphene-electrode-based resistive memory. Using a Raman raster scanning map, we verify that the transport direction of oxygen ions contributes to such dramatic differences in the device's switching characteristics.