Flexible synaptic floating gate devices with dual electrical modulation based on ambipolar black phosphorus

Two-dimensional van der Waals materials offer various possibilities for synaptic devices, matching the requirements of intelligent and energy-efficient computation. However, very few studies on robust flexible synaptic transistors have been reported, which hold great potential for soft robotics and wearable applications. Here a floating gate synaptic device based on ambipolar black phosphorus (BP) on a flexible substrate has been demonstrated with two working modes. The three-terminal mode, where the carriers are injected into the floating gate, shows a nonvolatile memory effect, whereas the two-terminal mode shows a quasi-nonvolatile memory effect. Remarkably, the synaptic device working on the three-terminal mode shows an excellent performance in the energy-efficient computation of sub-fJ/spike with a fast gate voltage response down to ∼10 ns. Furthermore, the flexible synaptic device exhibits good endurance under 5,000 bending cycles with a strain of ∼0.63%, suggesting great potential in flexible neuromorphic applications with low energy consumption.