Spray-Coated, Volatile and Nonvolatile, Two-Terminal, Resistive Switching Memory Devices Comprising Liquid-Exfoliated Black Phosphorus and Graphene Layers

Resistive switching memory devices fabricated with black phosphorus inks showed volatile memory device characteristics, specifically static random access memory (SRAM) and bipolar resistive switching. A high ON-/OFF-current ratio of 6.5 × 10 ⁷ was obtained at a reading voltage of 0.5 V with good retention stability (over 10 ⁴ s). Multilevel data storage performance under different compliance currents was demonstrated. Importantly, a nonvolatile memory device was also fabricated, using an ink that comprised thinner, on average, black phosphorus flakes with a narrower thickness distribution than the ink used in the above described devices. The nonvolatile memory device showed good write/erase operation, like flash memory, during 100 endurance cycles, and good retention stability with 1.9 × 10 ³ of on/off ratio at 0.5 V. According to these results, we suggest that thin films of liquid-exfoliated black phosphorus deposited by spray coating are suitable for low-cost, solution-processed, two-terminal resistive memory devices, either volatile or nonvolatile ones, the memory device type being controlled by the details of the ink preparation process, and the resulting flake thickness distributions.