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The use of an identical electrolyte in electrochemical metallization (ECM)-based neuron and synaptic devices has not yet been achieved due to their different resistive-switching characteristics. Herein, we describe ECM devices comprising the same ferroelectric PbZr0.52Ti0.48O3 (PZT) electrolyte, which can sustain both neuron and synaptic behavior depending on the identity of the active electrode. The Ag/PZT/La0.8Sr0.2MnO3 (LSMO) threshold switching memristor shows abrupt and volatile resistive switching characteristics, which lead to neuron devices with stochastic integration-and-fire behavior, auto-recovery, and rapid operation. In contrast, the Ni/PZT/LSMO memory switching memristor exhibits gradual, non-volatile resistive switching behavior, which leads to synaptic devices with a high on/off ratio, low on-state current, low variability, and spike-timing-dependent plasticity (STDP). The divergent behavior of the ECM devices is attributed to greater control of cation migration through the ultrathin ferroelectric PZT. Thus, ECM devices with an identical ferroelectric electrolyte offer promise as essential building blocks in the construction of high-performance neuromorphic computing systems.

As the amount of data has grown exponentially with the advent of artificial intelligence and the Internet of Things, computing systems with high energy efficiency, high scalability, and high processing speed are urgently required. Unlike traditional digital computing, which suffers from the von Neumann bottleneck, brain-inspired computing can provide efficient, parallel, and low-power computation based on analog changes in synaptic connections between neurons. Synapse nodes in brain-inspired computing have been typically implemented with dozens of silicon transistors, which is an energy-intensive and non-scalable approach. Ion-movement-based synaptic devices for brain-inspired computing have attracted increasing attention for mimicking the performance of the biological synapse in the human brain due to their low area and low energy costs. This paper discusses the recent development of ion-movement-based synaptic devices for hardware implementation of brain-inspired computing and their principles of operation. From the perspective of the device-level requirements for brain-inspired computing, we address the advantages, challenges, and future prospects associated with different types of ion-movement-based synaptic devices.

Next-generation electronic and optoelectronic devices require a high-quality channel layer. Graphene is a good candidate because of its high carrier mobility and unique ambipolar transport characteristics. However, the on/off ratio and photoresponsivity of graphene are typically low. Transition metal dichalcogenides (e.g., MoSe2) are semiconductors with high photoresponsivity but lower mobility than that of graphene. Here, we propose a graphene/MoSe2 barristor with a high-k ion-gel gate dielectric. It shows a high on/off ratio (3.3 × 104) and ambipolar behavior that is controlled by an external bias. The barristor exhibits very high external quantum efficiency (EQE, 66.3%) and photoresponsivity (285.0 mA/W). We demonstrate that an electric field applied to the gate electrode substantially modulates the photocurrent of the barristor, resulting in a high gate tuning ratio (1.50 μA/V). Therefore, this barristor shows potential for use as an ambipolar transistor with a high on/off ratio and a gate-tunable photodetector with a high EQE and responsivity. An approach that enhances control over charge carrier movement in graphene-based transistors may be useful in applications such as bendable circuits and light sensors. The difference in current flow when a transistor turns from on to off plays a critical role in determining device performance. Bae Ho Park from Konkuk University in Seoul, South Korea, and colleagues report that stacking graphene on top of another two-dimensional (2D) film of molybdenum selenide can lead to larger on/off current ratios than conventional graphene transistors. Optical and electrical characterizations revealed that the interface between the 2D films created a potential barrier that blocked current flow in the device’s off state without compromising graphene’s mechanical flexibility. Using an external voltage to modulate current flow through the barrier region also allowed the stacked device to serve as a high-efficiency photodetector. we report a field-effect device with a graphene/MoSe2 channel layer and high-k ion-gel gate dielectric. The device shows a high carrier mobility (~247 cm2/V ∙ s), a high on/off ratio (3.3 × 104), and ambipolar behavior that are controlled by an applied gate voltage. The strong gating effect of the device results in higher external quantum efficiency (EQE) (66.3%), photoresponsivity (285.0 mA/W), and gate-tuning ratio (1.50 μA/V) compared to pristine devices. Therefore, our graphene/MoSe2 barristor device can be a suitable candidate for use in ambipolar transistors and gate-tunable broad-area photodetectors.

In the era of "big data," the cognitive system of the human brain is being mimicked through hardware implementation of highly accurate neuromorphic computing by progressive weight update in synaptic electronics. Low-energy synaptic operation requires both low reading current and short operation time to be applicable to large-scale neuromorphic computing systems. In this study, an energy-efficient synaptic device is implemented comprising a Ni/Pb(Zr

We have fabricated Pt/ZrO2/Ir memory cells with pristine and Ar+ ion bombarded ZrO2 films, which show unipolar resistive switching behaviors. Ar+ ion bombardment induces change in surface morphology and chemical states of ZrO2 films. We have found that forming voltage significantly decreases in a Pt/ZrO2/Ir memory cell whose Ar+ ion bombarded ZrO2 film shows oxygen vacancy like defects and the largest root-mean-square (RMS) roughness. It seems that forming process may be more easily induced in an Ar+ ion bombarded ZrO2 film with higher RMS roughness mainly due to locally enhanced electric field in a region with oxygen vacancy like defects.

High-quality channel layer is required for next-generation flexible electronic devices. Graphene is a good candidate due to its high carrier mobility and unique ambipolar transport characteristics but typically shows a low on/off ratio caused by gapless band structure. Popularly investigated organic semiconductors, such as pentacene, suffer from poor carrier mobility. Here, we propose a graphene/pentacene channel layer with high-k ion-gel gate dielectric. The graphene/pentacene device shows both high on/off ratio and carrier mobility as well as excellent mechanical flexibility. Most importantly, it reveals ambipolar behaviors and related negative differential resistance, which are controlled by external bias. Therefore, our graphene/pentacene barristor with ion-gel gate dielectric can offer various flexible device applications with high performances.