Jing Zhang

Flexible Tellurium Nanorope Films

In article number 2300557, Tae Geun Kim and co-workers present hexagonal-shaped, ultrathin and highly flexible Te and Te–metal nanorope arrays grown by low-power radiofrequency (RF) sputtering. Blue organic light-emitting diodes (OLEDs) with 7-nm Te–W nanoropes as the anode exhibit significantly higher external quantum efficiencies, lower turn-on voltages and superior mechanical stabilities than indium-tin-oxide-based devices. The unique features of the Te-based nanorope film provide an effective outlet for multifunctional devices.

Nature Communications, Published online: 05 January 2024; doi:10.1038/s41467-023-44617-w

Here, the authors use three-layer boron nitride to construct interfacial ferro- and antiferroelectric tunnel junctions and find that the polarization is flipped in a layer-by-layer way, resulting in multiresistance states.

Nature Materials, Published online: 05 January 2024; doi:10.1038/s41563-023-01759-y

Multiferroics can possess multiple ferroic orders, for example, electric polarization and magnetism, and are of interest for new device applications. Here thermal control is shown to manipulate electric and magnetic orders in a single-phase quasi-two-dimensional halide perovskite.

This study aims to implement hydroxide ions for the modification of WS₂, facilitating the successful doping of various transition metals, such as Cr, Mn, Fe, Co, and Ni, into the WS₂ matrix. Dopant atoms affect the energy band structure of WS₂ and create more defects, which significantly affects the photoluminescence of pristine WS₂, providing potential applications in optoelectronics.

Abstract

Atomically doping in thin film poses a significant challenge due to the potential for dopant precipitation caused by self-purification effects. This challenge is particularly pronounced in the case of doping monolayers of photoluminescent transition metal dichalcogenides, where high energy barriers are also required to break the in-plane bonds between the transition metal (TM) and chalcogen atoms. To address this issue, this study introduces hydroxide ions to adsorb onto the surface of WS₂ monolayers. This results in a significant reduction in the formation energy of the TM─S bonds, enabling them to substitute for W sites and overcoming the self-purification effect of WS₂ monolayers. The in-plane doping of TMs including Cr, Mn, Fe, Co, and Ni atoms is confirmed through precise atomic-scale chemical imaging using scanning transmission electron microscopy with electron energy loss spectroscopy mapping. Photoluminescence measurements reveal that the band structure of WS₂ monolayers can be systematically modulated by different doping metals, owing to their distinct atomic sizes. In addition, the atomically-doped WS₂ monolayers exhibit room-temperature ferromagnetism, which has never been seen in pristine WS₂ monolayers. The modulation of the band structure and the emergence of magnetism in TMs-doped WS₂ monolayers hold significant promise for optoelectronic and magnetoelectric applications.

By precisely controlling the multiexciton emission of a hybrid manganese chloride doped with sb, a highly thermally stable compound with three emission colors (green, orange, yellow) has been developed. The optical temperature sensing, anti-counterfeiting and information encryption models based on the compound are designed.

Abstract

Recently, zero-dimensional (0D) metal halides with highly efficient tunable emission have shown broad prospects in the field of anti-counterfeiting. However, the limited emission colors and low resolution, as well as the severe thermal quenching of self-trapped excitons, have greatly constrained their applications. In this study, a high thermal stability compound by precisely manipulating the multi-exciton emission within Sb-doped hybrid manganese chloride is developed, which exhibits three emission colors (green, orange, and yellow). It is discovered that this compound exhibits significant color changes in the low-temperature range. Optical temperature sensing, anti-counterfeiting, and information encryption models based on this compound are successfully designed. This research proposes an effective strategy for designing novel eco-friendly and efficient anti-counterfeiting and temperature sensing materials, paving the way for optical temperature sensing and multi-key encryption-decryption applications.

Infrared scattering-type scanning near-field optical microscopy (s-SNOM) is used to investigate resistive switching in Ta₂O₅ films and reveals individual filaments on the device level of resistive random-access memories (ReRAMs). By selecting an appropriate illumination frequency, the simultaneous tracing of the evolution of filaments and the joule heating-induced retraction of the top electrode until device failure is possible.

Abstract

Resistive switching devices based on metal oxides are candidates for nonvolatile memory storage. They often rely on the valence change mechanism, the field-induced movement of donor ions leading to nanoscale conductive paths in filamentary-type devices. Devices usually consist of a transition metal oxide like Ta₂O₅ sandwiched between two metal electrodes. Critical parameters of the devices, such as cycle-to-cycle variability, R _off/R _on ratio, and endurance depend on the morphology and composition of the filaments. However, investigating filaments on the nanoscale is cumbersome, and commonly applied techniques such as conductive atomic force or transmission electron microscopy require delaminating the metal top electrode, inhibiting in operando investigations over many switching cycles. Here, the authors use infrared scattering-type scanning near-field optical microscopy (s-SNOM) to investigate resistive switching in Ta₂O₅ films with a graphene top electrode in operando and reveal individual filaments on the device level. By selecting an appropriate illumination frequency, the authors can trace the evolution of filaments and the joule heating-induced retraction of the top electrode until device failure. s-SNOM promises a deeper understanding of resistive switching devices’ microscopic switching behavior and applies to a wide range of resistive switching oxides, such as HfO₂, SrTiO₃, and SiO₂.

Taking inspiration from the scorpion slit receptors and the layered structure of the skin, a combined biomimetic strategy is adopted to prepare a continuous pressure positioning sensor. It can simultaneously monitor the magnitude and position of pressure and apply it to the field of human–computer interaction, achieving simple emotional communication.

Abstract

A high-performance flexible pressure sensor is one of the most important components of electronic skin, which can endow artificial devices with human-like capabilities. However, the electronic skin usually relies on the arrays of sensors to simultaneously obtain both pressure magnitude and position, making the data processing time-consuming, tedious, and error-prone. Here, a novel continuous pressure positioning sensor (PPS) with flexible multilayer structures based on a combinatorial bionic strategy is designed and fabricated. This PPS is composed of the pressure sensing layer (PSL) and the pressure positioning layer (PPL). The PSL exhibits high sensitivity (18.87 kPa⁻¹) owing to the bionic crack structures. Based on the connection/disconnection of the upper and lower conductive layers, this PPL exhibits excellent positioning properties with excellent resolution (≈35 µm). More importantly, due to stable signal change and synchronization of signals between the two functional layers (>21 pa), this PPS can recognize the type of signal. Applications of the PPS for pressure monitoring, tire safety monitoring, lunar rover road condition monitoring, and emotional communication in human–computer interaction are further demonstrated to measure magnitude, position, and recognition of pressure signals. So, it will have broad application prospects in fields such as pressure detection and human–computer interaction.

Organic frameworks-based memristors have aroused tremendous interests as promising candidates for novel in-memory computing technology. Here, this work provides a comprehensive review about the fundamentals and recent progress of organic frameworks-based memristors and their versatile applications for data storage, artificial synapses, and neuromorphic computation.

Abstract

Memristors have recently become powerful competitors toward artificial synapses and neuromorphic computation, arising from their structural and electrical similarity to biological synapses and neurons. From the diversity of materials, numerous organic and inorganic materials have proven to exhibit great potential in the application of memristors. Herein, this work focuses on a class of memristors based on organic frameworks (OFs) materials, and pay attention to the most advanced experimental demonstrations. First, the typical device structures and memristive switching mechanisms are introduced. Second, the latest progress of OFs-based memristors is comprehensively summarized, including metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and hydrogen-bonded organic frameworks (HOFs), as well as their applications in data storage, artificial synapses, and neuromorphic devices. Finally, the future challenges and prospects of OFs-based memristors are deeply discussed.

Nature Nanotechnology, Published online: 04 January 2024; doi:10.1038/s41565-023-01557-2

A metasurface-based approach is used to implement computationally expensive digital convolution operations in high-speed, low-power optics for improving the latency and power consumption of machine vision systems.

Nature Materials, Published online: 03 January 2024; doi:10.1038/s41563-023-01715-w

Peng Wu, Tianyi Zhang, Jiadi Zhu, Tomás Palacios and Jing Kong discuss the reproducibility issues in the synthesis and device fabrication of two-dimensional transition metal dichalcogenides that need to be addressed to enable the lab-to-fab transition.

Monolayer Fe2C is expected to possess strong electronic correlations, which can significantly contribute to electronic and magnetic properties. In this study we consider electronic and magnetic properties of MXene Fe2C within the DFT+DMFT approach. We establish the existence of local magnetic moments \mu_{\mathrm{loc}} = 3.3\,\mu_B in this compound, characterized by sufficiently long lifetime of \tau\sim 350 fs. We also calculate exchange interaction parameters accounting for electronic correlations using the recently developed approach for paramagnetic phase. At low temperatures, we obtain the strongest exchange interaction 11 meV between next nearest neighboring Fe atoms, located above (or below) the carbon plane, and the subleading interaction 6 meV between the next to next nearest neighboring atoms, located across the carbon plane. The resulting dependence of the Berzinskii–Kosterlitz–Thouless (BKT) and Curie temperatures on magnetic anisotropy is obtained. The BKT temperature for the pristine Fe2C is T_{\mathrm{BKT}}\simeq 300 K, which makes this compound a good candidate for the two-dimensional ferromagnet with XY anisotropy.

Nature, Published online: 03 January 2024; doi:10.1038/d41586-023-03671-6

High-entropy ceramics can be transformative for several applications, but the development of this class of materials is limited by costly and time-consuming experimental processes. The disordered enthalpy–entropy descriptor is a mathematical formula that accelerates the computational discovery of synthesizable high-entropy ceramics, and has already guided the synthesis of nine new high-entropy carbonitrides and borides.

Nature, Published online: 03 January 2024; doi:10.1038/s41586-023-06908-6

We report atomic observations of six incoherent twin boundary configurations and structural transitions in diamond at room temperature, showing a dislocation-mediated mechanism different from metallic systems and shedding new light on grain boundary behaviour.

Nature, Published online: 03 January 2024; doi:10.1038/s41586-023-06858-z

We measure efficient heat conductance through the electrically insulating quantum Hall bulk and propose a theoretical model based on the role played by the localized states.

Nature, Published online: 03 January 2024; doi:10.1038/s41586-023-06811-0

Semiconducting epigraphene aligned with single-crystal silicon carbide substrates has a band gap of 0.6  eV and room temperature mobilities 20 times larger than that of other two-dimensional semiconductors, making it suitable for nanoelectronics.

Nature Nanotechnology, Published online: 03 January 2024; doi:10.1038/s41565-023-01567-0

Here, 3D nanofabrication and elasticity programming of monolithic soft microrobots equipped with magnetic springs with strain response at piconewton forces capable of deformation on micrometre length scales is demonstrated for applications in cell force sensing, cell manipulation and soft actuation.

Nature Nanotechnology, Published online: 04 January 2024; doi:10.1038/s41565-023-01579-w

By preadsorption of water molecules on a material surface, a controllable ångström-scale van der Waals (vdW) gap is created, which can be applied to other vdW material systems with controllable gaps.

Nature Synthesis, Published online: 02 January 2024; doi:10.1038/s44160-023-00443-y

Rapid, long-distance transport of an ultrathin and uniform palladium film on a two-dimensional (2D) crystal of tungsten ditelluride at accessible temperatures is reported. The surprising effect is generalizable and offers possibilities for exploring chemical synthesis in nanoconfined spaces and access to not yet synthesized 2D materials.

Nature Electronics, Published online: 02 January 2024; doi:10.1038/s41928-023-01109-5

An acoustic resonator that uses a three-dimensional silicon fin and an atomic-layered hafnia-zirconia ferroelectric transducer can be integrated into chip-scale filter arrays to make adaptive switch-free spectral processors for wireless communication.

This review paper focuses on memristor-based neuromorphic chips, which provide an extensive description of the working principle and characteristic features of memristors, along with their applications in the realm of neuromorphic chips. Additionally, the key performance metrics of the chip is highlighted, as well as the key metrics related to the memristor devices are employed to realize both the synaptic and neuronal components.

Abstract

In the era of information, characterized by an exponential growth in data volume and an escalating level of data abstraction, there has been a substantial focus on brain-like chips, which are known for their robust processing power and energy-efficient operation. Memristors are widely acknowledged as the optimal electronic devices for the realization of neuromorphic computing, due to their innate ability to emulate the interconnection and information transfer processes witnessed among neurons. This review paper focuses on memristor-based neuromorphic chips, which provide an extensive description of the working principle and characteristic features of memristors, along with their applications in the realm of neuromorphic chips. Subsequently, a thorough discussion of the memristor array, which serves as the pivotal component of the neuromorphic chip, as well as an examination of the present mainstream neural networks, is delved. Furthermore, the design of the neuromorphic chip is categorized into three crucial sections, including synapse-neuron cores, networks on chip (NoC), and neural network design. Finally, the key performance metrics of the chip is highlighted, as well as the key metrics related to the memristor devices are employed to realize both the synaptic and neuronal components.

A freeze-tolerant conductive organohydrogel is fabricated by in situ forming charged polar terminal groups and a water–ethylene glycol binary solvent system. The prepared organohydrogel is ultra-stretchable (≈6185%), tough (9.2 MJ m⁻³), highly transparent (≈99%), freeze-tolerant (−78 °C), self-adhesive (10.2–27.8 kPa) and biocompatible. It is applied to low-temperature adaptive wearable devices with delay-free signals even at −40 °C.

Abstract

Wearable electronics based on conductive hydrogels (CHs) easily suffer from prolonged response times, reduced wearing comfort, shortened service lives, and impaired signal accuracy in cold environments, because conventional CHs tend to freeze at subzero temperatures and lose their flexibility, adhesion, transparency, and conductivity, which will limit their applications in extreme environments. Inspired by the way psychrotolerant creatures and superabsorbent materials interfere with the hydrogen bonding networks of water, a freeze-resistant conductive organohydrogel (COH) is facilely fabricated. The synergy effect between charged polar terminal groups and a binary solvent system of water–ethylene glycol weakens the hydrogen bonding between water molecules and endows the COH with remarkable freezing tolerance (−78 °C). Additionally, the obtained COH is ultra-stretchable (≈6185%), tough (9.2 MJ m⁻³), highly transparent (≈99%), self-adhesive (10.2–27.8 kPa), and biocompatible. This versatile COH is assembled into a strain sensor and a well-designed bracelet electrocardiogram sensor. Benefiting from the exceptional low-temperature tolerance of the prepared COH, these devices exhibit fast response with delay-free signals even at −40 °C. Overall, this work proposes a strategy to develop multifunctional COHs for supporting human health in cold environments.

Skin-Like Temperature Sensors

In article number 2305252, Tae Il Lee, Jin Young Oh, and co-workers present an intrinsically stretchable subthreshold organic transistor for a skin-like temperature sensor. The transistor working in the subthreshold region enables highly sensitive temperature sensing with the highest transconductance efficiency at near zero voltage, which leads to ultralow power consumption. This allows for skin-like temperature sensors with active matrix arrays that map the temperature distribution under 3D deformation.

Nature Nanotechnology, Published online: 02 January 2024; doi:10.1038/s41565-023-01574-1

An atomically thin indium tin oxide film in the form of a quantum well exhibits a χ2 of ~1,800 pm V–1. Theoretical calculations point to an asymmetric electronic interband transition resonance as the reason for this large χ2 value.

The superior performance of electrochemiluminescence (ECL) in bioanalysis with high sensitivity and broad dynamic range exhibits excellent potential for low-abundant microRNA (miRNA) detection. Therefore, the versatile ECL-based biosensors for miRNA detection are summarized, and as an important part, the signal amplification strategies integrated with ECL are also elaborated.

Abstract

Electrochemiluminescence (ECL) as an analytical technology with a perfect combination of electrochemistry and spectroscopy has received considerable attention in bioanalysis due to its high sensitivity and broad dynamic range. Given the selectivity of bio-recognition elements and the high sensitivity of the ECL analysis technique, ECL biosensors are powerful platforms for the sensitive detection of biomarkers, achieving the accurate prognosis and diagnosis of diseases. MicroRNAs (miRNAs) are crucial biomarkers involved in a variety of physiological and pathological processes, whose aberrant expression is often related to serious diseases, especially cancers. ECL biosensors can fulfill the highly sensitive and selective requirements for accurate miRNA detection, prompting this review. The ECL mechanisms are initially introduced and subsequently categorize the ECL biosensors for miRNA detection in terms of the quenching agents. Furthermore, the work highlights the signal amplification strategies for enhancing ECL signal to improve the sensitivity of miRNA detection and finally concludes by looking at the challenges and opportunities in ECL biosensors for miRNA detection.

A method to prepare large-scale vertically interconnected CFETs based on a thermal evaporation process is reported. The thermally-evaporated Te and Bi₂S₃ are chosen to serve as p-type and n-type semiconductor channels. The CFET inverter exhibits a clear switching behavior, indicating that thermal evaporation provides a powerful and reliable route to facilitate vertically stacked CMOS circuits.

Abstract

With the rapid development of integrated circuits, there is an increasing need to boost transistor density. In addition to shrinking the device size to the atomic scale, vertically stacked interlayer interconnection technology is also an effective solution. However, realizing large-scale vertically interconnected complementary field-effect transistors (CFETs) has never been easy. Currently-used semiconductor channel synthesis and doping technologies often suffer from complex fabrication processes, poor vertical integration, low device yield, and inability to large-scale production. Here, a method to prepare large-scale vertically interconnected CFETs based on a thermal evaporation process is reported. Thermally-evaporated etching-free Te and Bi₂S₃ serve as p-type and n-type semiconductor channels and exhibit FET on-off ratios of 10³ and 10⁵, respectively. The vertically interconnected CFET inverter exhibits a clear switching behavior with a voltage gain of 17 at a 4 V supply voltage and a device yield of 100%. Based on the ability of thermal evaporation to prepare large-scale uniform semiconductor channels on arbitrary surfaces, repeated upward manufacturing can realize multi-level interlayer interconnection integrated circuits.

Within the search for new low dimensional antiferromagnetic materials, it is shown how on-surface synthesis allows to fabricate 2D metal–organic coordination networks (Co-HOB) with a strong antiferromagnetic coupling between the Co centers and perpendicular anisotropy.

Abstract

Antiferromagnetic spintronics is a rapidly emerging field with the potential to revolutionize the way information is stored and processed. One of the key challenges in this field is the development of novel 2D antiferromagnetic materials. In this paper, the first on-surface synthesis of a Co-directed metal–organic network is reported in which the Co atoms are strongly antiferromagnetically coupled, while featuring a perpendicular magnetic anisotropy. This material is a promising candidate for future antiferromagnetic spintronic devices, as it combines the advantages of 2D and metal–organic chemistry with strong antiferromagnetic order and perpendicular magnetic anisotropy.

This work demonstrated a method for coplanar epitaxial growth of single crystals of arbitrarily shaped 2H-MoTe₂ on the etched edges of MoS₂ to obtain coplanar MoS₂−MoTe₂ heterostructures with the same crystal orientation. Furthermore, scanning transmission electron microscopy and fast Fourier transform indicate that MoTe₂ inherits the crystal orientation of MoS₂ and is seamlessly stitched with it.

Abstract

Two-dimensional (2D) coplanar heterostructure enables high-performance optoelectronic devices, such as p–n heterojunctions. However, realizing site-controllable and shape-specific 2D coplanar heterojunctions composed of two semiconductors with the same crystal orientation still requires the development of new growth methods. Here, a route to fabricate MoS₂–MoTe₂ coplanar heterojunctions with the same crystal orientation is reported by exploiting the properties of phase transition and atomic rearrangement during the growth of 2H-MoTe₂. Raman spectroscopy and electron microscopy techniques reveal the chemical composition and lattice structure of the heterostructure. Both MoS₂ and MoTe₂ in the heterojunction are single crystals and have the same lattice orientation, and their shapes can be arbitrarily defined by electron beam lithography. Electrical measurements show that the MoS₂ and MoTe₂ channels exhibit n-type and p-type transfer characteristics, respectively. The coplanar epitaxy technology can be used to prepare more coplanar heterostructures with novel device functions.

Versatile photoluminescence supramolecular polymers are constructed, which incorporate abundant hydrogen bonds, disulfide bonds, and aggregation-induced emission (AIE) molecules into dynamic hard domains of polymers for integrating self-healing ability, mechanical strength, and fluorescence responsiveness. Printed diversified patterns on polymer substrates exhibit dual-mode upconversion emission, enabling the development of functional optical devices with self-healing and fluorescence information encoding capabilities, demonstrating potential applications.

Abstract

The development of comprehensive optical self-healing polyurethane polymers for smart optical devices presents a significant challenge due to the trade-off between intrinsic self-healing capability and mechanical strength. This study focuses on the synthesis of versatile photoluminescence supramolecular polymers that integrate self-healing ability, mechanical strength, and fluorescence responsiveness. The incorporation of hydrogen bonds and disulfide bonds into the dynamic hard domain results in the optimal polymer exhibiting impressive mechanical properties (strength, 27.0 MPa; toughness, 132.1 MJ m⁻³; elongation at break, 1450%), as well as a conspicuous self-healing efficiency (surface scratches disappear within just 1 min). Furthermore, the transparent (transparency >97%) and colorless polymers demonstrate aggregation-induced emission, characterized by intense cyan fluorescence that transitions to subdued blue fluorescence upon stretching under 365 nm irradiation. Proof-of-concept experiments demonstrate that screen-printed fluorescent patterns, based on as-prepared fluorescence ink associated with dual-mode upconversion emission, are able to successfully encode fluorescence information, and can be integrated into the self-healable 3D optical devices. The self-healing optical devices designed with versatile polymers and featuring diversified patterns offer a promising direction for the advancement and application of future self-healing materials.