Fig. 1. (Color online) Characterization and performance of the GFST. (a) The structure of GFST. (b) Raman spectra of transferred graphene. (c) AFM images of graphene and graphene/F₁₆CuPc, the R_q values of graphene and graphene/F₁₆CuPc were 3.32 and 1.11 nm. (d) The electronic band structures of transferred graphene and graphene/F₁₆CuPc. (e) Transfer curves of GFST under different sweep direction, under V_DS = ±0.01 V. (f) Output curves of GFST. The operating region of GFST can be divided into four cases (Case #1−4).

Fig. 2. (Color online) Emulation of excitatory postsynaptic current based on GFST. Schematic illustrations of the cell membrane potential of postneuron (a) and the information transfer at biological synapse (b). (c) EPSCs triggered by different electrical spikes (±4 V, 50 ms) at V_DS of ±0.01 V. EPSC of GFST could be emulated in all the four cases.

Fig. 3. (Color online) Multiplexed neurotransmitter transmission based on GFST. (a) Selective release of two excitatory neurotransmitters is emulated by applying gate voltages with different magnitude and polarity, where the V_DS is −0.01 V. (b) PPF of the GFST triggered by two consecutive spikes with time intervals varying from 0.05 to 3.2 s. (c) PPF index versus time intervals between two consecutive spikes.

Fig. 4. (Color online) Synaptic plasticity regulation based on GFST. (a) Spike-number-dependent plasticity of the GFST. (b) The decay trend of ΔEPSC within 200 s after the application of different numbers of external spikes. (c) The retention rate of EPSC within 200 s after triggered by 100 external spikes. (d) and (e) Image encryption-decryption process triggered by two types of spike stimuli.

Fig. 5. (Color online) Validation of the learning capability of GFST and application in artificial neural networks. (a) Complementary synaptic transistor arrays for neural network. (b) Neural network structure for image recognition of Fashion-MNIST dataset. (c) Synaptic potentiation and depression of GFST under Case #1 (electron-dominated EPSC), Case #2 (hole-dominated EPSC). (d) The conductance changes of GFST under Case #1, Case #2 and the complementary of the two cases. (e) Recognition rate of images recognition.