Electrolyte‐Gated Synaptic Transistor with Oxygen Ions

Abstract

Artificial synaptic devices are the essential hardware of neuromorphic computing systems, which can simultaneously perform signal processing and information storage between two neighboring artificial neurons. Emerging electrolyte-gated transistors have attracted much attention for efficient synaptic emulation by using an addition gate terminal. Here, an electrolyte-gated synaptic device based on the SrCoO x (SCO) films is proposed. It is demonstrated that the reversible modulation of SCO phase transforms the brownmillerite SrCoO 2.5 and perovskite SrCoO 3−δ , through controlling the insertion and extraction of oxygen ions with electrolyte gating. Nonvolatile multilevel conduction states can be realized in the SCO films following this route. The synaptic functions such as the long-term potentiation and depression of synaptic weight, spike-timing-dependent plasticity, as well as spiking logic operations in the device are successfully mimicked. These results provide an alternative avenue for future neuromorphic devices via electrolyte-gated transistors with oxygen ions.

Filament‐Free Bulk Resistive Memory Enables Deterministic Analogue Switching

“…Moreover, switching is linear and symmetric, essential attributes required to achieve high network training accuracy: [ 1,34,36 ] Crossbar simulations (Cross‐Sim [ 36 ] ) show ≈97% training accuracy for the MNIST training set (Figure S6, Supporting Information). While this device is a type of electrochemical random‐access memory (ECRAM), [ 40–50 ] the bulk‐RRAM cells based on oxygen vacancies presented here provide significant advantages in terms of scalability, retention, and CMOS compatibility over previously developed ECRAM, and will be discussed later.…”

“…This contrasts strongly with other types of ECRAM cells, which also have three terminals but that need electronic switches to isolate the gate from the channel. [ 40–50 ] We plot the memory loss over time ( Figure a) when shorting the base and switching layers after setting the device to a high‐conductance state. The switching layer decay time strongly depends on temperature: at room temperature, it decays less than 0.3% after one week.…”

“…Whereas bulk‐RRAM cells retain state by immobilizing and blocking ion migration, ECRAM cells that operate at constant temperature instead use electronic switches to block electron migration between the gate and channel. [ 40–50 ] This method does not scale well for smaller devices: R OFF is constant and depends on the properties of the switch while C decreases proportionally with the area (Figure 4e). Assuming that R OFF ≈ 10 13 Ω (ref.…”

“…Another class of analogue memory with significant recent research is ECRAM [ 40–50 ] based on bulk transport of Li + or H + defects. Our statistical ensemble analysis also explains why these ECRAM switch more linearly and deterministically than filamentary devices.…”

“…Moreover, there are wide numbers of CMOS‐compatible materials that conduct oxygen vacancies at elevated temperatures, including many transition metal oxides. ECRAM that switches at room temperature must utilize more mobile defect ions like Li + in metal oxides, [ 41,44,46 ] H + in electroactive polymers, [ 42,45 ] or O 2− in ionic liquids, [ 40,48 ] which often necessitates CMOS‐incompatible materials.…”