High-performance flexible resistive random access memory devices based on graphene oxidized with a perpendicular oxidation gradient.

The conventional strategy of fabricating resistive random access memory (RRAM) based on graphene oxide is limited to a resistive layer with homogeneous oxidation, and the switching behavior relies on its redox reaction with an active metal electrode, so the obtained RRAMs are typically plagued by inferior performance and reliability. Here, we report a strategy to develop high-performance flexible RRAMs by using graphene oxidized with a perpendicular oxidation gradient as the resistive layer. In contrast to a homogeneous oxide, this graphene together with its distinctive inter-layer oxygen diffusion path enables excellent oxygen ion/vacancy diffusion. Without an interfacial redox reaction, oxygen ions can diffuse to form conductive filaments with two inert metal electrodes by applying a bias voltage. Compared with state-of-the-art graphene oxide RRAMs, these graphene RRAMs have shown superior performance including a high on-off current ratio of ∼105, long-term retention of ∼106 s, reproducibility over 104 cycles and long-term flexibility at a bending strain of 0.6%, indicating that the material has great potential in wearable smart data-storage devices.