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. 2020 Oct 13;23(11):101676. doi: 10.1016/j.isci.2020.101676

Figure 4.

Figure 4

Representative Images Showing the Working Principles of Synaptic Devices: Atom Switches, Charge Trapping/Detrapping, Gate-Tunable Memristors, Defect (Vacancies) Engineering

(A) (i) Schematic representation of a graphene-based atom switch using a lateral nanogap. (ii) I-V characteristics of a graphene nanogap (3 nm) atom switch during the low-bias switching in ambient conditions. Reprinted with permission from (Sarwat et al., 2017). Copyright 2017 American Chemical Society.

(B) (i) Schematic representation of a diode-type 2D vertically stacked MoS2/h-BN/graphene heterostructure (two-terminal floating-gate memory) via charge trapping/detrapping. (ii) Cross-sectional bright-field STEM and EDS elemental mapping of the device with 10-nm hr-BN. (iii) Schematic illustration of electron tunneling between the electrode and the graphene floating gate that shows the memory operation during a program state. (iv) Schematic illustration of the memory operation during an erase state. Reprinted with permission from (Vu et al., 2016). Copyright 2016 Springer Nature.

(C) (i) Schematic illustration of a CVD-grown 2D monolayer MoS2 memtransistor device built on SiO2 (300 nm) on doped Si (gate). (ii) ID-VD curves for 10 consecutive sweeps at each gate bias (VG) that show the gate-tunability. (iii) I-V curve between terminals 2 and 4 of a six-terminal MoS2 memtransistor (left inset) at constant VG = 20 V. The right inset showing heterosynaptic plasticity observed by reversibly changing the conductance. Reprinted with permission from (Sangwan et al., 2018). Copyright 2018 Springer Nature.

(D) (i) Schematic representation of the irradiation strategy for post-growth defect engineering. (ii) Optical micrograph of a CVD-grown 2D monolayer MoS2 memtransistor fabricated by localized He+ beam irradiation. (iii) TEM image of the irradiated (red) fissure region and adjacent (green and blue) regions on a mechanically exfoliated suspended few-layer MoS2 sample. Reprinted with permission from (Jadwiszczak et al., 2019). Copyright 2019 American Chemical Society.