Resistive switching characteristics of graphene/NiO/highly ordered pyrolytic graphite resistive random access memory capacitors

Polycrystalline NiO thin films were deposited on single crystalline HOPG substrates via radio frequency sputtering. On the HOPG substrate, the NiO thin film exhibited (111) and (222) X-ray diffraction peaks, thereby indicating that the film was polycrystalline. The graphene/NiO/HOPG RRAM capacitor showed canonical RRAM behavior, which was confirmed by evaluating the electrical properties of RRAM switching curves, writing endurance tests, retention tests, and SET and RESET voltages as a function of switching cycles. In particular, the graphene/NiO/HOPG RRAM capacitor exhibited lower SET and RESET voltages than the Pt/NiO/Pt RRAM capacitor, resulting from of the low work function of graphene and HOPG electrodes. In addition, it was possible to reduce the dispersion of the LRS and HRS states and the SET and RESET voltages for repeated switching cycles. It was suggested that this small dispersion was influenced by the simple configuration of the conducting filaments as well as the low interface roughness values of the graphene/NiO/HOPG capacitor.