Memristors with nonvolatile memory characteristics have been expected to open a new era for neuromorphic computing and digital logic. However, existing memristor devices based on oxygen vacancy or metal‐ion conductive filament mechanisms generally have large operating currents, which are difficult to meet low‐power consumption requirements. Therefore, it is very necessary to develop new materials to realize memristor devices that are different from the mechanisms of oxygen vacancy or metal‐ion conductive filaments to realize low‐power operation. Herein, high‐performance and low‐power consumption memristors based on 2D WS2 with 2H phase are demonstrated, which show fast ON (OFF) switching times of 13 ns (14 ns), low program current of 1 µA in the ON state, and SET (RESET) energy reaching the level of femtojoules. Moreover, the memristor can mimic basic biological synaptic functions. Importantly, it is proposed that the generation of sulfur and tungsten vacancies and electron hopping between vacancies are dominantly responsible for the resistance switching performance. Density functional theory calculations show that the defect states formed by sulfur and tungsten vacancies are at deep levels, which prevent charge leakage and facilitate the realization of low‐power consumption for neuromorphic computing application.

α-NaFeO2 is promising as minor-metal free cathode materials for low cost sodium-ion batteries. It has a flat voltage plateau at 3.3 V vs. Na metal and a stable reversible capacity of 85 mAh g−1. Fe3+/Fe4+ redox reaction on charge/discharge cycle was confirmed by 57Fe Mössbauer spectrometer. The thermal stability of NaFeO2 cathodes with/without 1 mol dm−3 NaClO4/EC-DMC electrolyte was investigated by DSC measurements. The fully-charged Na0.58FeO2 powder decomposed thermally at a temperature higher than 300°C, with Fe2O3 as a possible product. On the other hand, the mixture of Na0.58FeO2 powder and electrolyte showed exothermic heat in a temperature range of 220–300°C. However, NaFeO2 showed better thermal stability in the electrolyte than LiCoO2 counterparts in Li ion battery systems, including less heat generation and higher exothermic onset temperature. This indicated that the Na-ion batteries might have comparable thermal stability with Li-ion batteries.

Resistive switching (RS) is a promising emerging storage technology that has received much attention due to its many advantages, such as economy, fast operating speed, long retention, high density, and low energy consumption. [1] RS effects are widely applied in the fields of nonvolatile RS random access memory (RRAM), artificial neural computing, and reconfigurable logic operations and so on. [2] RRAM memories based on electrochemical metallization (ECM) and valance change mechanism (VCM) are commonly used for the memristor application. [3] Compared with conventional computing based on the von Neumann architecture, memristor (i.e., RS device) computing is proving to be superior for brain-inspired computing, such as image processing and speech recognition, [2] where the diffusion of the metal ions such as Ag + , Cu + , or oxygen vacancies are used to mimic the diffusion of Ca + in the neural cell. [4] However, the switching voltages in the memristor devices (MDs) showWith the advent of the era of big data, resistive random access memory (RRAM) has become one of the most promising nanoscale memristor devices (MDs) for storing huge amounts of information. However, the switching voltage of the RRAM MDs shows a very broad distribution due to the random formation of the conductive filaments. Here, selfassembled lead sulfide (PbS) quantum dots (QDs) are used to improve the uniformity of switching parameters of RRAM, which is very simple comparing with other methods. The resistive switching (RS) properties of the MD with the self-assembled PbS QDs exhibit better performance than those of MDs with pure-Ga 2 O 3 and randomly distributed PbS QDs, such as a reduced threshold voltage, uniformly distributed SET and RESET voltages, robust retention, fast response time, and low power consumption. This enhanced performance may be attributed to the ordered arrangement of the PbS QDs in the self-assembled PbS QDs which can efficiently guide the growth direction for the conducting filaments. Moreover, biosynaptic functions and plasticity, are implemented successfully in the MD with the self-assembled PbS QDs. This work offers a new method of improving memristor performance, which can significantly expand existing applications and facilitate the development of artificial neural systems. Data Storage

Light emission from biased tunnel junctions has recently gained much attention owing to its unique potential to create ultracompact optical sources with terahertz modulation bandwidth 1-5. The emission originates from an inelastic electron tunnelling process in which electronic energy is transferred to surface plasmon polaritons and subsequently converted to radiation photons by an optical antenna. Because most of the electrons tunnel elastically, the emission efficiency is typically about 10 −5-10 −4. Here, we demonstrate efficient light generation from enhanced inelastic tunnelling using nanocrystals assembled into metal-insulator-metal junctions. The colour of the emitted light is determined by the optical antenna and thus can be tuned by the geometry of the junction structures. The efficiency of far-field free-space light generation reaches ~2%, showing an improvement of two orders of magnitude over previous work 3,4. This brings on-chip ultrafast and ultracompact light sources one step closer to reality. Electrons can tunnel through a metal-insulator-metal (MIM) junction either elastically or inelastically. For elastic tunnelling, electrons tunnel across the barrier layer without energy loss 6. However, the inelastic tunnelling process may create either phonons or photons as the electrons lose part of their energy in the gap and transition to a lower energy state in the metal counter-electrode. This process can be enhanced in the presence of surface plasmon polaritons around the MIM junction, as first discovered in 1976 1. Later theoretical 2 and experimental 7-10 studies increased the appeal of the MIM junction because of its ultra-small footprint and ultra-large modulation bandwidth. However, the main challenge for light generation from inelastic electron tunnelling is its low external quantum efficiency (EQE), a production of internal quantum efficiency (IQE) and radiation efficiency. Generally, the IQE describes the efficiency of the inelastic tunnelling event and can be increased by designing a plasmonic structure with a large local density of optical states (LDOS) 7,11,12 , and the radiation efficiency can be improved by introducing a high-quality optical antenna 13,14. Recently, light emission from electrically driven optical antennas made by amorphous (polycrystalline) plasmonic material has been demonstrated 3,4 with quantum efficiencies up to 10 −4. Compared with amorphous or polycrystalline plasmonic material, single-crystalline material has lower plasmonic loss 15 , which can further enhance the performance of the inelastic tunnel junction. Here, we use single-crystalline silver (Ag) nanocrystals to form tunnel junctions with gap distances of ~1.5 nm. Through geometrical engineering of the junctions to optimize the LDOS and radiation efficiency, we obtain a far-field light that the device could be integrated into photonics and/or plasmonic systems for on-chip applications 23-26. In principle, the emission frequency of the MIM junction device could cover a range from ultraviolet to mid-infrared, a...

We demonstrate an ultra-high-bandwidth Mach-Zehnder electro-optic modulator (EOM), based on foundry-fabricated silicon (Si) photonics, made using conventional lithography and wafer-scale fabrication, oxide-bonded at 200C to a lithium niobate (LN) thin film. Our design integrates silicon photonics light input/output and optical components, such as directional couplers and low-radius bends. No etching or patterning of the thin film LN is required. This hybrid Si-LN MZM achieves beyond 106 GHz 3-dB electrical modulation bandwidth, the highest of any silicon photonic or lithium niobate (phase) modulator.

We report measurements of time-frequency entangled photon pairs and heralded single photons at telecommunications wavelengths, generated using a periodically-poled, lithium niobate on insulator (LNOI) waveguide pumped optically by a diode laser. We achieve a high Coincidences-to-Accidentals Ratio (CAR) at high pair brightness, a low value of the conditional self-correlation function [g (2) (0)], and high two-photon energy-time Franson interferometric visibility, which demonstrate the high quality of the entangled photon pairs and heralded single photons.

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The development of the information age has made resistive random access memory (RRAM) a critical nanoscale memristor device (MD). However, due to the randomness of the area formed by the conductive filaments (CFs), the RRAM MD still suffers from a problem of insufficient reliability. In this study, the memristor of Ag/ ZrO 2 /WS 2 /Pt structure is proposed for the first time, and a layer of two-dimensional (2D) WS 2 nanosheets was inserted into the MD to form 2D material and oxide double-layer MD (2DOMD) to improve the reliability of single-layer devices. The results indicate that the electrochemical metallization memory cell exhibits a highly stable memristive switching and concentrated ON-and OFF-state voltage distribution, high speed (∼10 ns), and robust endurance (>10 9 cycles). This result is superior to MDs with a single-layer ZrO 2 or WS 2 film because two layers have different ion transport rates, thereby limiting the rupture/rejuvenation of CFs to the bilayer interface region, which can greatly reduce the randomness of CFs in MDs. Moreover, we used the handwritten recognition dataset (i.e., the Modified National Institute of Standards and Technology (MNIST) database) for neuromorphic simulations. Furthermore, biosynaptic functions and plasticity, including spike-timing-dependent plasticity and paired-pulse facilitation, have been successfully achieved. By incorporating 2D materials and oxides into a doublelayer MD, the practical application of RRAM MD can be significantly enhanced to facilitate the development of artificial synapses for brain-enhanced computing systems in the future.