Activating Silent Synapses in Sulfurized Indium Selenide for Neuromorphic Computing

Abstract

The transformation from silent to functional synapses is accompanied by the evolutionary process of human brain development and is essential to hardware implementation of the evolutionary artificial neural network but remains a challenge for mimicking silent to functional synapse activation. Here, we developed a simple approach to successfully realize activation of silent to functional synapses by controlled sulfurization of chemical vapor deposition-grown indium selenide crystals. The underlying mechanism is attributed to the migration of sulfur anions introduced by sulfurization. One of our most important findings is that the functional synaptic behaviors can be modulated by the degree of sulfurization and temperature. In addition, the essential synaptic behaviors including potentiation/depression, paired-pulse facilitation, and spikerate-dependent plasticity are successfully implemented in the partially sulfurized functional synaptic device. The developed simple approach of introducing sulfur anions in layered selenide opens an effective new avenue to realize activation of silent synapses for application in evolutionary artificial neural networks.

Thermally Tunable Analog Memristive Behaviors in Sulfurized In2Se3 Nanoflakes for Bio-Plausible Synaptic Devices

“…Therefore, few selenium vacancies would be generated in pristine In 2 Se 3 owing to the large formation energy compared with that of sulfurized In 2 Se 3 . That can well explain the difficulty in observing memristive behavior in pristine In 2 Se 3 , as shown in Figure S4 and our previous work …”

“…It is expected to achieve both analog and digital memristive behaviors by synergistically utilizing anion migration and ferroelectricity mechanisms, which should be studied deeply in the future. The memristive behaviors significantly become stronger with the increase in temperature, which increases the complexity of the memristor and thus helps to realize dynamic functionalities. , It is noteworthy that the memristive device is much robustness since it can work at elevated temperatures as high as 550 K, in accordance with the conclusion of the AIMD simulation above. Figure e–g presents autorelaxation processes of the device at different temperatures after DC operations.…”

“…That can well explain the difficulty in observing memristive behavior in pristine In 2 Se 3 , as shown in Figure S4 and our previous work. 25 The transition state (TS) search based on DFT theory was further carried out to evaluate the migration barriers of selenium and sulfur vacancies at the atomic scale, as shown in Figure 4c,d, respectively. For simplicity, we take two adjacent positions as the initial state (IS) and final state (FS), and the energies of IS have been set to zero.…”

“…Figure a presents that the synaptic device shows ultrafast responsivity upon single stimuli pulse with a voltage amplitude of 50 mV and pulse width of 10 μs. The energy consumption for single pulse events can be estimated by V × I × Δ t , in which V , I , and Δ t denote the amplitude of the stimuli pulse, the value of excitonic current, and pulse width, respectively. , Considering that the performed condition is at the high temperature of 550 K, the estimated energy consumption of ∼92.5 fJ is much small . Note that the thickness of SiO 2 for the SiO 2 /Si substrate is 1 μm which is thick enough to avoid the issue of gate leakage current.…”

Synaptic Transistor Based on In‐Ga‐Zn‐O Channel and Trap Layers with Highly Linear Conductance Modulation for Neuromorphic Computing

“…So far, there have been many attempts to implement synaptic devices such as memtransistor, [ 12 ] phase‐change memories , [ 13,14 ] and metal oxide resistive memories. [ 15–17 ] Especially, resistive memories can have multiple conductance states by forming filaments.…”