Artificial Synaptic Emulators Based on MoS₂ Flash Memory Devices with Double Floating Gates

Abstract

We fabricated MoS-based flash memory devices by stacking MoS and hexagonal boron nitride (hBN) layers on an hBN/Au substrate and demonstrated that these devices can emulate various biological synaptic functions, including potentiation and depression processes, spike-rate-dependent plasticity, and spike-timing dependent plasticity. In particular, compared to a flash memory device prepared on an hBN substrate, the device fabricated on the hBN/Au exhibited considerably more symmetric and linear bidirectional gradual conductance change curves, which may be attributed to the device structure incorporating double floating gate. For the device on the hBN/Au, electron transfers may occur between the floating gate MoS and Au, as well as between the floating gate MoS and the channel MoS, allowing for more control over electron tunneling and injection. To test our hypothesis, we also fabricated a MoS-based flash memory device on an hBN/Pd substrate and found behavior similar to the device fabricated on hBN/Au. Our results demonstrate that flexible synaptic electronics may be implemented using MoS-based flash memory devices with double floating gates.

Dual‐Gated MoS2 Memtransistor Crossbar Array

“…[12,37] In conventional neuromorphic learning algorithms, linear and symmetric weight update rules not only enable higher accuracy in classification tasks, but can also simplify the training process by enabling blind update protocols. [12b,13a,b] Several approaches have been previously employed to improve the linearity and symmetry of two-ter-minal memristors, including modifying pulse writing schemes in organic electrochemical transistors, [13c] designing multilayer floating gates in MoS 2 synaptic transistors, [38] controlling filament saturation in epitaxial SiGe memristors, [39] and using an additional tunnel barrier or different contact metals in metaloxide memristors. [13a,b] Broadly, these approaches either modify the device materials in a manner that introduces other device performance tradeoffs or require changes to the pulsing protocol that complicates time-domain multiplexing during training.…”

Stimuli‐Enabled Artificial Synapses for Neuromorphic Perception: Progress and Perspectives

“…A synaptic device with double FGs shows improved linearity and symmetry in its conductance change properties, which is beneficial for improved pattern recognition accuracy in neuromorphic computing. [82] As shown schematically in Figure 3e, Yi et al [83] designed a device structure that used MoS 2 and Interface-type devices based on the electron/hole transfer mechanism. a) Working mechanism of the memristor device: programming at 35V, off-state reading at 5 V, erasure at −50 V,, and on-state reading at 5 V. The reading current in the pentacene channel is modulated by hole trapping/ detrapping in the PVN layer near the short Cu electrode.…”

Two-Dimensional Near-Atom-Thickness Materials for Emerging Neuromorphic Devices and Applications

“…The device is based on the trapping or detrapping of electrons in the WCL on h-BN with an O 2 plasma treatment, which modulates the WSe 2 channel conductivity ( Seo et al., 2018 ). Many other studies also utilized 2D MoS 2 layers in heterostructures based on charge trapping/detrapping mechanisms ( Chen et al., 2019a ; Kim et al., 2019c ; Paul et al., 2019 ; Wang et al., 2019b ; Yi et al., 2018 ).…”

“…Their desirable properties, including atomic thickness, dangling-bond-free surfaces, mechanical strength, high integration density, tunable electrical transport, and optical properties, as well as low energy consumption, make them ideal candidates for applications in a wide range of electronic devices ( Gupta et al., 2015 ; Mas-Ballesté et al., 2011 ; Xia et al., 2017 ). More recently, the applications of 2D materials have been extensively studied for energy-efficient and high-performing artificial synapses ( Arnold et al., 2017 ; Chen et al., 2019c ; Dev et al., 2020 ; Hu et al., 2019 ; Jiang et al., 2017 ; Kalita et al., 2019 ; Kim et al., 2019c ; Krishnaprasad et al., 2019 ; Kumar et al., 2019 ; Li et al., 2018 ; Liu et al., 2019 ; Mao et al., 2019 ; Paul et al., 2019 ; Pradhan et al., 2020 ; Xie et al., 2018a , 2018b ; Xu et al., 2019 ; Yan et al., 2019a ; Yi et al., 2018 ; Zhu et al., 2019 ). Furthermore, owing to their dangling-bonds-free surface and atomically thin nature, a variety of 2D materials-based heterostructures have been developed in spite of their lattice mismatch ( Novoselov et al., 2016 ).…”