Jiuxiang Dai

Nature, Published online: 28 March 2023; doi:10.1038/d41586-023-00878-5

A design strategy that relies on virtual lattices allows scientists to recreate biological shapes in a wide variety of materials.

npj 2D Materials and Applications, Published online: 29 March 2023; doi:10.1038/s41699-023-00384-2

Unconventional conductivity increase in multilayer black phosphorus

npj 2D Materials and Applications, Published online: 29 March 2023; doi:10.1038/s41699-023-00383-3

Extreme mechanical tunability in suspended MoS₂ resonator controlled by Joule heating

Journal of Applied Physics, Volume 133, Issue 12, March 2023.

Applied Physics Letters, Volume 122, Issue 13, March 2023.
Self-powered ultraviolet (UV) photodetectors (PDs) based on GaN have been of great importance in the application of UV communication, thanks to its wide direct bandgap and strong resistance to irradiation. However, current self-powered GaN-based heterojunction UV photodetectors could not meet the requirement of fast photoresponse. Herein, type-II pn heterojunction GaS/GaN-based self-powered PDs have been proposed with a naturally p-type doping GaS thin film grown on n-type GaN via chemical vapor deposition. The electronic and optical properties of GaS/GaN heterojunction were investigated via experiments and the density functional theory. Afterward, as-prepared GaS/GaN-based PDs reveal an excellent self-powered photosensitivity/detectivity of 6.26 mA W−1/8.29 × 109 Jones at 0 V at 365 nm, ultrafast response speed with a rise/fall time of 48/80 μs as well as an amazing rejection ratio (R365 nm/R500 nm) of 3.42 × 104, and a fine rectification ratio of 105.9. This work provides a feasible method to synthesize high-performance GaS/GaN heterojunctions and demonstrates their enormous potential in ultrafast response self-powered UV photodetection.

Applied Physics Letters, Volume 122, Issue 13, March 2023.
Despite its scalability and CMOS process compatibility, the limited endurance and sub-optimal stress response of ferroelectric Zr-substituted hafnia [(Hf,Zr)O2] have been one of the key impediments toward its integration into practical device and technology applications. Here, using electrical measurements complemented by photoluminescence spectroscopy, we investigate the underlying mechanisms behind this behavior in 10 nm thick W/Hf0.5Zr0.5O2/W capacitors. Analyzing the evolution of leakage current with stress cycles and the spectroscopic response of the stress-induced leakage current, we attribute the behavior to defect levels, which lie at 0.6 eV from the conduction band edge of the ferroelectric. Photoluminescence spectroscopy, in turn, further corroborates the defect level's position within the bandgap while enabling its attribution to the presence of oxygen vacancies. This work helps to identify oxygen vacancies as the key factor responsible for the degraded endurance and stress response in (Hf,Zr)O2 and subsequently motivates the exploration of methods to reduce the oxygen vacancy concentrations without destabilizing the ferroelectric orthorhombic phase.

Metal–organic frameworks are ideal candidates for applying Patterson functions to determine the positions of the metal atoms within the crystallographic unit cell. In addition, the internal network structure—defined by the linker molecules—can be identified. The method is applied to solve the crystal structure of a new thin film polymorph of copper-isonicotinate.

Abstract

The preparation of thin films is often associated with the appearance of unknown polymorphs, as both the substrate and deposition method can heavily influence crystallization processes. Here, chemical vapor deposition is used to obtain thin films of a copper-isonicotinate (Cu-INA) metal–organic framework (MOF). Starting from copper-based precursor layers (copper oxide and hydroxide), a solid-vapor conversion with vaporized isonicotinic acid in either a dry or humidified atmosphere, yields a new Cu-INA MOF polymorph. It is found that the crystalline order of the precursor layer has a strong impact on the texture of Cu-INA thin films. Furthermore, a novel methodology is introduced to determine the structure of a previously unknown thin-film phase of Cu-INA. Although only a few diffraction peaks are found via synchrotron grazing incidence X-ray diffraction (GIXRD), a triclinic unit cell can be determined, and Patterson functions can be calculated. The latter reveals the position of the copper atoms within the unit cell and the alignment of the INA linkers defining the coordination network structure. This work introduces how the combination of GIXRD data with Patterson functions can be used to identify the structure of an unknown thin-film MOF polymorph.

This account summarizes the recent progress of low dimensional sulfur nanomaterials including 0D sulfur nanoparticles (SNPs), sulfur nanodots (SNDs), sulfur quantum dots (SQDs), 1D sulfur nanorods (SNRs), and 2D sulfur nanosheets (SNSs), paying attention to the synthetic method, characterization and properties, formation mechanism, surface functionalization, and applications of these sulfur nanomaterials. as well as the prospect and challenges in emerging fields.

Abstract

Low-dimensional sulfur nanomaterials featuring with 0D sulfur nanoparticles (SNPs), sulfur nanodots (SNDs) and sulfur quantum dots (SQDs), 1D sulfur nanorods (SNRs), and 2D sulfur nanosheets (SNSs) have emerged as an environmentally friendly, biocompatible class of metal-free nanomaterials, sparking extensive interest in a wide range application. In this review, various synthetic methods, precise characterization, creative formation mechanism, delicate functionalization, and versatile applications of low dimensional sulfur nanomaterials over the last decades are systematically summarized. Initially, it is striven to summarize the progress of low dimensional sulfur nanomaterials from versatile precursors by using different synthetic approaches and various characterization. Then, a multi-faceted proposed formation mechanism with emphasis on how these different precursors produce corresponding SNPs, SNDs, SQDs, SNRs, and SNSs is highlighted. Besides, it is essential to fine-tune the surface functional groups of low dimensional sulfur nanomaterials to form new complex nanomaterials. Finally, these sulfur nanomaterials are being investigated in bio-sensing, bio-imaging, lithium–sulfur batteries, antibacterial activities, plant growth along with future perspective and challenges in emerging fields. The purpose of this review is to tailor low dimensional nanomaterials through accurately selecting precursors or synthetic approach and provide a foundation for the formation of versatile sulfur nanostructure.

Advanced Materials, Volume 35, Issue 13, March 29, 2023.

Nature, Published online: 29 March 2023; doi:10.1038/d41586-023-00724-8

The number of distinguishable conductance levels in memristor devices — electronic components that store information without power — has been limited by noise. An understanding of the source of the noise, and development of an effective denoising process, have now enabled 2,048 conductance levels to be achieved in memristors in large arrays fabricated in a chip factory.

Nature, Published online: 29 March 2023; doi:10.1038/d41586-023-00730-w

A generalizable technique has been developed to create diverse functional inorganic membranes on the surface of various aqueous solutions. The technique ensures that the air–liquid interface receives a continuous supply of floating particles, which then assemble dynamically to form continuous membranes.

Applied Physics Letters, Volume 122, Issue 13, March 2023.
Two-dimensional (2D) multiferroic materials with robust magnetoelectric coupling and controllable topological solitons (such as skyrmions) are promising candidates for advanced information storage and processing. Due to the limitations of experimental techniques, first-principles investigations stand out in answering fundamental questions of 2D multiferroic couplings, thus providing guidance for experimental validation. Herein, we will give a review of recent theoretical progress in the exploration of 2D multiferroic coupling via structural design and molecular engineering approach. Particularly, we will focus on (i) how to design the multiferroic structure in the 2D form; (ii) how to achieve robust magnetoelectric coupling; and (iii) how to electrically control the magnetic skyrmion via multiferroic effects. Finally, we give some perspectives on the remaining challenges and opportunities for predicting 2D multiferroic materials.

Nature Synthesis, Published online: 30 March 2023; doi:10.1038/s44160-023-00281-y

A lack of guiding principles limits the preparation of two-dimensional (2D) materials prepared by a solution-phase growth route. Now, a general qualitative model for 2D material growth is proposed and applied to fabricate more than 30 nanomaterials, allowing 2D growth to be controlled by only tuning the reaction concentration or temperature.

Nature Nanotechnology, Published online: 30 March 2023; doi:10.1038/s41565-023-01355-w

The crystallization of nanoparticles is observed with single-particle resolution via electron microscopy. The growth modes are explained via computer simulations, unifying the understanding of crystallization from the atomic to micrometre scale.

Highly stable single-layer 2D assemblies of Au^I-thiolate, with both long-range molecular order and a uniform triangular morphology, have been synthesized, and their elastic and anisotropic curling upon external stimuli has been achieved on single-assembly level.

Abstract

Synthesis of highly stable two-dimensional single-layer assemblies (SLAs) is a key challenge in supramolecular science, especially those with long-range molecular order and well-defined morphology. Here, thin (thickness <2 nm) triangular Au^I-thiolate SLAs with high thermo-, solvato- and mechano- stability have been synthesized via a double-ligand co-assembly strategy. Furthermore, the SLAs show assembly-level elastic and anisotropic deformation responses to external stimuli as a result of the long-range anisotropic molecular packing, which provides SLAs with new application potentials in bio-mimic nanomechanics.

A high-performance, high-stability, and low-cost Te_0.7Se_0.3 infrared photodiode is fabricated throughcomplementary metal–oxide–semiconductor (CMOS)-compatible low-temperature thermal evaporation. The device achieves the fastest response among Te-based photodiodes, a low dark current density , the ability of matter identification, and superior electrical and thermal stabilities. This work paves a new way for CMOS-compatible infrared imagers.

Abstract

Short-wave infrared detectors are increasingly important in the fields of autonomous driving, food safety, disease diagnosis, and scientific research. However, mature short-wave infrared cameras such as InGaAs have the disadvantage of complex heterogeneous integration with complementary metal–oxide–semiconductor (CMOS) readout circuits, leading to high cost and low imaging resolution. Herein, a low-cost, high-performance, and high-stability Te _x Se_{1– x} short-wave infrared photodiode detector is reported. The Te _x Se_{1– x} thin film is fabricated through CMOS-compatible low-temperature evaporation and post-annealing process, showcasing the potential of direct integration on the readout circuit. The device demonstrates a broad-spectrum response of 300–1600 nm, a room-temperature specific detectivity of 1.0 × 10¹⁰ Jones, a −3 dB bandwidth up to 116 kHz, and a linear dynamic range of over 55 dB, achieving the fastest response among Te-based photodiode devices and a dark current density 7 orders of magnitude smaller than Te-based photoconductive and field-effect transistor devices. With a simple Si₃N₄ packaging, the detector shows high electric stability and thermal stability, meeting the requirements for vehicular applications. Based on the optimized Te _x Se_{1– x} photodiode detector, the applications in material identification and masking imaging is demonstrated. This work paves a new way for CMOS-compatible infrared imaging chips.

The primary challenge that ferroelectric field-effect transistors face is their vulnerability to the repeated program/erase cycle. To solve this issue, an efficient self-curing method is presented. The proposed method successfully recovers synaptic fatigue damage, enhancing learning accuracy in the convolutional neural network.

Abstract

With the recently increasing prevalence of deep learning, both academia and industry exhibit substantial interest in neuromorphic computing, which mimics the functional and structural features of the human brain. To realize neuromorphic computing, an energy-efficient and reliable artificial synapse must be developed. In this study, the synaptic ferroelectric field-effect-transistor (FeFET) array is fabricated as a component of a neuromorphic convolutional neural network. Beyond the single transistor level, the long-term potentiation and depression of synaptic weights are achieved at the array level, and a successful program-inhibiting operation is demonstrated in the synaptic array, achieving a learning accuracy of 79.84% on the Canadian Institute for Advanced Research (CIFAR)-10 dataset. Furthermore, an efficient self-curing method is proposed to improve the endurance of the FeFET array by tenfold, utilizing the punch-through current inherent to the device. Low-frequency noise spectroscopy is employed to quantitatively evaluate the curing efficiency of the proposed self-curing method. The results of this study provide a method to fabricate and operate reliable synaptic FeFET arrays, thereby paving the way for further development of ferroelectric-based neuromorphic computing.

Moiré superlattice structure appears with the mutual slippage of two-dimensional layered materials. It can modulate the electronic structure and the electron density distribution, induce active edge states as well as regulate the band structure of 2D layered materials, which thus endow 2D layered materials with excellent catalytic properties.

Abstract

Two-dimensional (2D) layered materials have been widely used as catalysts due to their high specific surface area, large fraction of uncoordinated surface atoms, and high charge carrier mobility. Moiré superlattice emerges in 2D layered materials with twist angle or lattice mismatch. By manipulating the moiré superlattice structure, 2D layered materials present modulated electronic band structure, topological edge states, and unconventional superconductivity which are tightly associated with the performance of catalysts. Hence, engineering moiré superlattice structures are proposed to be an important technology in modifying 2D layered materials for improved catalytic properties. However, currently, the investigation of moiré superlattice structure in a catalytic application is still in its infancy. This perspective starts with the discussion of structural features and fabrication strategy of 2D materials with moiré superlattice structure. Afterward, the catalytic applications, including electrocatalytic and photocatalytic applications, are summarized. In particular, the promotion mechanism of the catalytic performance caused by the moiré superlattice structure is proposed. Finally, the perspective is concluded by outlining the remaining challenges and possible solutions for the future development of 2D materials with moiré superlattice structure towards the catalytic applications.

Herein, a high-entropy oxide (HEO) anchored 2D Ti₃C₂T_x MXene (HEO/Ti₃C₂T_x) hybrid via impregnation and microwave-heating methods is developed. The attained HEO/Ti₃C₂T_x-0.5 hybrid achieved a comparable oxygen evolution reactions (OER) performance with the commercial IrO₂ catalyst with/without visible-light illumination. Furthermore, the fabricated water electrolyzer with HEO/Ti₃C₂T_x-0.5 hybrid as anode required a low potential of 1.62 V to drive 10 mA cm^-2 under visible-light illumination.

Abstract

High-entropy oxides (HEO) have recently concerned interest as the most promising electrocatalytic materials for oxygen evolution reactions (OER). In this work, a new strategy to the synthesis of HEO nanostructures on Ti₃C₂T_x MXene via rapid microwave heating and subsequent calcination at a low temperature is reported. Furthermore, the influence of HEO loading on Ti₃C₂T_x MXene is investigated toward OER performance with and without visible-light illumination in an alkaline medium. The obtained HEO/Ti₃C₂T_x-0.5 hybrid exhibited an outstanding photoelectrochemical OER ability with a low overpotential of 331 mV at 10 mA cm⁻² and a small Tafel slope of 71 mV dec⁻¹, which exceeded that of a commercial IrO₂ catalyst (340 mV at 10 mA cm⁻²). In particular, the fabricated water electrolyzer with the HEO/Ti₃C₂T_x-0.5 hybrid as anode required a less potential of 1.62 V at 10 mA cm⁻² under visible-light illumination. Owing to the strong synergistic interaction between the HEO and Ti₃C₂T_x MXene, the HEO/Ti₃C₂T_x hybrid has a great electrochemical surface area, many metal active sites, high conductivity, and fast reaction kinetics, resulting in an excellent OER performance. This study offers an efficient strategy for synthesizing HEO-based materials with high OER performance to produce high-value hydrogen fuel.

Nature Electronics, Published online: 28 March 2023; doi:10.1038/s41928-023-00945-9

AI chips that flip