Controlled oxidation levels in graphene oxide to achieve forming-free and analog resistive switching in RRAM

In the exploration of materials for neuromorphic computing, Graphene Oxide (GO) stands out as a promising organic candidate due to its low-cost fabrication, flexibility, and tunable chemical properties. However, the underlying mechanisms of resistive switching in GO remain unclear. We believe that previous studies may have undervalued the role of GO as the resistive switching medium, focusing instead on various metallic electrodes. In this study, we designed experiments to pinpoint the origin of resistive switching in Graphene Oxide-based Resistive Switching Random Access Memories (RRAM). To investigate the resistive switching mechanisms, we fabricated GO-based RRAMs with three different levels of oxidation: high (3), medium (1.5), and low (0.5). Comparisons using X-ray diffraction analysis (XRD), Raman spectroscopy, and Fourier Transform Infrared (FTIR) spectroscopy confirmed successful adjustments in functional groups, which are expected to play a role in the resistive switching phenomena within GO. The devices created demonstrated stable SET/RESET cycles, with an endurance of 10² cycles and a retention time of 10⁴ seconds. Modifying the oxidation levels unveiled forming-free and analog resistive switching capabilities for the GO(1.5) devices, accompanied by minimal variability—an essential feature for neuromorphic computing. Furthermore, the overshoot transition during the SET process exhibited a slope that was 2.5 times lower for the GO(1.5) RRAM, which is crucial for linear synaptic evolution. We also observed a direct correlation between the Ion/Ioff ratio and oxidation concentration, indicating that oxygen-based functional groups within the GO layers are key components in the resistive switching behavior of these devices. In conclusion, we propose a multifilamentary mechanism for resistive switching that accounts for the differing electrical characteristics of medium and highly oxidized GO-RRAMs.