Jing Zhang

CoCl₂/Co₃O₄ heterojunctions are obtained on Si/SiO₂ substrates with the assistance of supercritical CO₂ (SC CO₂), and the prepared samples have significantly higher coercivity and saturation magnetization intensity.

Abstract

As a remarkable structure, 2D magnetic heterojunctions have attracted researchers’ attention owing to their controlled manipulation in the electronic device. However, successful fabrication as well as modulation of their structure and compound remain challenging. Herein, a novel method is designed to obtain a CoCl₂/Co₃O₄ heterojunction on Si/SiO₂ substrate with the assistance of supercritical CO₂ (SC CO₂), and the as-fabricated sample has significantly increased coercivity and saturation magnetization, which is 11 times higher than pure Co₃O₄. Further, it can be found that the CO₂ pressure has the decisive effect on the saturation magnetization of the sample. Therefore, it suggests that the tunable electronic-magnetic device can be anticipated to be obtained in the future.

Nature Photonics, Published online: 31 October 2023; doi:10.1038/s41566-023-01317-7

Combining photoacoustic excitation with optomechanics enables the mechanical modes associated with entire microorganisms to be detected, demonstrating that mechanical spectroscopy allows us to identify microorganisms and characterize their life stages.

Nature Communications, Published online: 02 November 2023; doi:10.1038/s41467-023-42821-2

Recently, a Luttinger liquid state was reported in a moiré superlattice of bilayer tungsten ditelluride at small twist angles and temperatures of a few kelvins. Here, the authors extend this result to millikelvin temperatures, supporting the existence of the 2D anisotropic Luttinger liquid as a stable ground state.

Nature Materials, Published online: 31 October 2023; doi:10.1038/s41563-023-01731-w

Integrated design assisted by materials and technology innovations can help a transition from traditional to sustainable electronics.

Nature, Published online: 02 November 2023; doi:10.1038/d41586-023-03353-3

Device can wield tools inside one of the heart’s chambers while bracing itself against a stabilizer fitted into a major cardiac vein.

Bioinspired large-area atomically-thin graphene membranes exhibit distinct mechanical performances that provide an opportunity for modularization because the fiber-reinforced network composite structure is like a shell of “concrete” wrapping outside the graphene membrane. The nanoporous graphene membrane, after reinforcement, maintains a prominent separation performance of the breathable function with an ultrahigh gas permeance and an ultralow water vapor transportation rate.

Abstract

Nanoporous graphene membranes are attractive for molecular separations, but it remains challenging to maintain sufficient mechanical strength during scalable fabrication and module development. Inspired by the composite structure of cell membranes and cell walls, a large-area atomically thin nanoporous graphene membrane supported by a fiber-reinforced structure with strong interlamellar adhesion is designed. Compared with other graphene-based membranes of large scale, the fracture stress, fracture strength, and tensile stiffness of the composite membranes can be enhanced by a factor of 17, 67, and 94, respectively. This fiber-reinforced structure also confers stability of the composite membrane to different curvature states and repeated bending processes after 10 000 times, which provides an opportunity for modularization. The breathable function of such membrane with an ultrahigh gas permeance (≈8.6–23 L m⁻² d⁻¹ Pa⁻¹) and an ultralow water vapor transportation rate (WVTR) (≈23–129 g L m⁻² d⁻¹) is observed, superior to most commercial materials. This work provides a facile method to fabricate large-area graphene membranes and paves the road to practical application in the membrane separation field for other 2D films.

The recent progress of negative capacitance (NC) field effect transistors (FETs) with ferroelectric gate stack is summarized in this review, including the related concepts for in-depth understanding of NC FETs. Moreover, some high-performance NC FETs with different ferroelectric gate stacks are presented. Finally, influential factors and challenges for improving 2D NC FETs are proposed.

Abstract

Steep subthreshold swing (SS) is a decisive index for low energy consumption devices. However, the SS of conventional field effect transistors (FETs) has suffered from Boltzmann Tyranny, which limits the scaling of SS to sub-60 mV dec⁻¹ at room temperature. Ferroelectric gate stack with negative capacitance (NC) is proved to reduce the SS effectively by the amplification of the gate voltage. With the application of 2D ferroelectric materials, the NC FETs can be further improved in performance and downscaled to a smaller dimension as well. This review introduces some related concepts for in-depth understanding of NC FETs, including the NC, internal gate voltage, SS, negative drain-induced barrier lowering, negative differential resistance, single-domain state, and multi-domain state. Meanwhile, this work summarizes the recent advances of the 2D NC FETs. Moreover, the electrical characteristics of some high-performance NC FETs are expressed as well. The factors which affect the performance of the 2D NC FETs are also presented in this paper. Finally, this work gives a brief summary and outlook for the 2D NC FETs.

Nature Photonics, Published online: 30 October 2023; doi:10.1038/s41566-023-01308-8

Event-based sensors enable super-resolution single-molecule localization microscopy with comparable quality and resolution to traditional scientific cameras, while also overcoming the limitations of high-density imaging.

A marsupial robotic system combining a continuum robot (mother robot) with nanorobots (child robots) is developed for cross-scale targeting drug delivery. The robotic system improves the targeting rate and therapeutic efficacy in brain tumor treatment with the hierarchical targeting strategy spanning targeting scale from centimeters to nanometers.

Abstract

Nanorobots capable of active movement are an exciting technology for targeted therapeutic intervention. However, the extensive motion range and hindrance of the blood–brain barrier impeded their clinical translation in glioblastoma therapy. Here, a marsupial robotic system constructed by integrating chemical/magnetic hybrid nanorobots (child robots) with a miniature magnetic continuum robot (mother robot) for intracranial cross-scale targeting drug delivery is reported. For primary targeting on macroscale, the continuum robot enters the cranial cavity through a minimally invasive channel (e.g., Ommaya device) in the skull and transports the nanorobots to pathogenic regions. Upon circumventing the blood–brain barrier, the released nanorobots perform secondary targeting on microscale to further enhance the spatial resolution of drug delivery. In vitro experiments against primary glioblastoma cells derived from different patients are conducted for personalized treatment guidance. The operation feasibility within organisms is shown in ex vivo swine brain experiments. The biosafety of the treatment system is suggested in in vivo experiments. Owing to the hierarchical targeting method, the targeting rate, targeting accuracy, and treatment efficacy have improved greatly. The marsupial robotic system offers a novel intracranial local therapeutic strategy and constitutes a key milestone in the development of glioblastoma treatment platforms.

Ferroelectric Field-Effect Transistors

Because of their simple structure and operation scheme based on characteristic spontaneous polarization, ferroelectric field-effect-transistors (FeFETs), which are reviewed by Jinseong Heo, Min Hyuk Park, and co-workers in article number 2204904, are considered promising for ultrahigh-density information storage with high speed and power efficiency. A post-3D-NAND structure based on the FeFET is shown.

PbI₂ is a unique 2D charge trap medium to offer atomically smooth interfaces, uniformly distributed traps and high-integration feasibility for reliable memories and artificial synapses. The spontaneously formed iodine vacancies in PbI₂ cause the charge trapping/releasing in 2D semiconducting channel such as MoS₂, WS₂, and WSe₂, leading to the significantly better comprehensive performance compared to previous 2D charge trap memories.

Abstract

Charge trap materials that can store carriers efficiently and controllably are desired for memory applications. 2D materials are promising for highly compacted and reliable memory mainly due to their ease of constructing atomically uniform interfaces, however, remain unexplored as being charge trap media. Here it is discovered that 2D semiconducting PbI₂ is an excellent charge trap material for nonvolatile memory and artificial synapses. It is simple to construct PbI₂-based charge trap devices since no complicated synthesis or additional defect manufacturing are required. As a demonstration, MoS₂/PbI₂ device exhibits a large memory window of 120 V, fast write speed of 5 µs, high on-off ratio around 10⁶, multilevel memory of over 8 distinct states, high reliability with endurance up to 10⁴ cycles and retention over 1.2 × 10⁴ s. It is envisioned that PbI₂ with ionic activity caused by the natively formed iodine vacancies is unique to combine with unlimited 2D materials for versatile van der Waals devices with high-integration and multifunctionality.

This review summarizes the recent development of smart textile optoelectronics for human-interfaced logic systems. Smart logic textile drives a new blueprint for textile optoelectronics from a single “Neuron” to a textile “Brain,” offering an ideal human-interfaced platform for next-generation wearable logic systems toward long-time and user-friendly human–machine interactions in response to sophisticated commands.

Abstract

Textiles with a freedom of form factor, unlimited scalability, and high programmability provide an ideal platform for constructing wearable optoelectronic systems. The emerging wearable technologies, like artificial intelligence and Internet of Things, have driven the development of textile optoelectronics from simple functional blocks to sophisticated logic systems, offering a seamless, breathable, and programmable on-body platform to synergistically sense, analyze, store, and feedback information in response to complex commands. In the past few years, the creation of such smart textile optoelectronics-based logic systems is boosted by nanomaterial science and manufacturing integration technologies and has revolutionized human–machine interaction paradigms in numerous emerging fields. Herein, in this review, the recent progress of smart textile optoelectronics for human-interfaced logic systems is timely summarized. This review begins with a concise discussion about the wearability evaluation and integration consideration of textile optoelectronic devices. Then, important breakthroughs in human-interfaced logic systems based on smart textile optoelectronics are demonstrated by highlighting their representative device, working principle, and application scenarios. Finally, the existing challenges and potential directions in the field of textile optoelectronics-integrated logic systems are analyzed.

Electrospinning-derived aligned IGZO (a-IGZO) NFN FETs are achieved. The superior electrical performance of the transistors is comparable to devices of the same type fabricated in high-temperature processes. The successful assembly of multi-scenario devices based on a-IGZO FETs also confirms thepotential of electrospun highly oriented inorganic fiber arrays obtained in low-temperature processes forapplications in nano-integrated circuits andvarious functional devices.

Abstract

Metal oxide field-effect transistors (MOFETs) represent a promising technology for applications in existing but alsoemerging large-area electronics. Simultaneously, the rise of 1D nanomaterials with unique properties, represented by nanofibers (NFs), has also energized research. Thus, developing 1D nanofiber networks (NFNs) to act as the potential building blocks for use in fundamental elements of transistors is considered to be a promising approach torealize high-performance 1D electronics. However, high processing temperatures and disordered nanofiber distribution represent two remaining technical challenges. Here, electrospun highly aligned IGZO (a-IGZO) nanofiber arrays with low-thermal-budget of 350 °C and impressive device characteristics are achieved, including a μFE of 5.63 cm2 V^–1 s^–1 and superior on/off current ratio of ≈107. When ALD-derived high-k HfAlOx thin films are employed as gate dielectrics, the source/drain voltage (VDS) can be substantially reduced by ten times to a range of only 03 V, along with a three times improvement in mobility to a respectable value of 15.9 cm2 V^–1 s^–1. Successful integrations of logic operation, sensor, and flexible devices implies the potential prospect of a-IGZO NFN FETs in multifunctional electronics. The strategy for combining cryogenic processes and parallel arrays provides a feasible and reliable route in building future low-power, high-performance flexible electronics.

This study introduces a biosensing device composed of Tin sulfide (SnS₂) and h-BN crystals for streptavidin detection. Researchers incorporate a biotin-based supporter construct conjugated with Pyrene–Lysine, effectively capturing the target analyte. Device performance is validated by Raman spectroscopy and electrical characterizations, which detect 0.5 pm streptavidin in 13.2 s.

Abstract

The exclusive features of two-dimensional (2D) semiconductors, such as high surface-to-volume ratios, tunable electronic properties, and biocompatibility, provide promising opportunities for developing highly sensitive biosensors. However, developing practical biosensors that can promptly detect low concentrations of target analytes remains a challenging task. Here, a field-effect-transistor comprising n-type transition metal dichalcogenide tin disulfide (SnS₂) is developed over the hexagonal boron nitride (h-BN) for the detection of streptavidin protein (Strep.) as a target analyte. A self-designed receptor based on the pyrene-lysine conjugated with biotin (PLCB) is utilized to maintain the sensitivity of the SnS₂/h-BN FET because of the π–π stacking. The detection capabilities of SnS₂/h-BN FET are investigated using both Raman spectroscopy and electrical characterizations. The real-time electrical measurements exhibit that the SnS₂/h-BN FET is capable of detecting streptavidin at a remarkably low concentration of 0.5 pm, within 13.2 s. Additionally, the selectivity of the device is investigated by measuring its response against a Cow-like serum egg white protein (BSA), having a comparative molecular weight to that of the streptavidin. These results indicate a high sensitivity and rapid response of SnS₂/h-BN biosensor against the selective proteins, which can have significant implications in several fields including point-of-care diagnostics, drug discovery, and environmental monitoring.

The advantages of nanodevices in structure analysis, field-effect regulation, in situ monitoring, and simulation modeling of low-dimensional electrocatalytic materials are introduced. It also emphasizes its multi-disciplinary and interdisciplinary application. A unique view on the prospects and improvement of nano-devices is given.

Abstract

Clean and sustainable energy conversion and storage through electrochemistry shows great promise as an alternative to traditional fuel or fossil-consumption energy systems. With regards to practical and high-efficient electrochemistry application, the rational design of active sites and the accurate description of mechanism remain a challenge. Toward this end, in this Perspective, a unique on-chip micro/nano device coupling nanofabrication and low-dimensional electrochemical materials is presented, in which material structure analysis, field-effect regulation, in situ monitoring, and simulation modeling are highlighted. The critical mechanisms that influence electrochemical response are discussed, and how on-chip micro/nano device distinguishes itself is emphasized. The key challenges and opportunities of on-chip electrochemical platforms are also provided through the Perspective.

As a new approach to “More than Moore”, a stretchable and transparent ionic display module of the integrated ionic circuit is successfully prepared. It is programmed to excite the hydrogel color change by a Faraday process occurring at specific pixel points. The display module exhibits stable performance under strong magnetic field conditions.

Abstract

As a new approach to “More than Moore”, integrated ionic circuits serve as a possible alternative to traditional electronic circuits, yet the integrated ionic circuit composed of functional ionic elements and ionic connections is still challenging. Herein, a stretchable and transparent ionic display module of the integrated ionic circuit has been successfully prepared and demonstrated by pixelating a proton-responsive hydrogel. It is programmed to excite the hydrogel color change by a Faraday process occurring at the electrode at the specific pixel points, which enables the display of digital information and even color information. Importantly, the display module exhibits stable performance under strong magnetic field conditions (1.7 T). The transparent and stretchable nature of such ionic modules also allows them to be utilized in a broad range of scenarios, which paves the way for integrated ionic circuits.

Optical comb lasers could increase data transmission rates in telecommunications

Nature Electronics, Published online: 26 October 2023; doi:10.1038/s41928-023-01052-5

Five-stage ring oscillators that operate at frequencies of up to 2.65 GHz can be created using monolayer molybdenum disulfide field-effect transistors developed with a design-technology co-optimization process.

There is a great prospect for termination-free MXene (MX) in catalysis, energy, and environmental applications. Beyond the currently and widely studied MXene, the termination-free MXs, high-entropy MXs, and MX-supported single atoms enable a huge spectrum of new and unique functional properties for targeted applications, to be developed in the coming few years.

Abstract

The fast ever-growing interest in transition metal carbonitrides (MXenes) for energy and catalysis is undermined by the undesirable multi-surficial terminations, which severely limit their applications. In contrast, considering the intriguing and tunable electronic structure, rich surface active sites, and high thermal durability, termination-free MXene (MX) hosts a huge possibility for catalysis. As such, recent advances in the evolution from MAX to MXene, and then to MX are overviewed and compared briefly, before concentrating on the unique future of MX in multi-heterogeneous catalysis. This work also looks beyond the fundamental properties of MX and discusses the potential of such materials for applications in multi-electron redox reactions. It is convinced that the potential success of MX in future catalysis is promising. Further extension toward high entropy and single-atom modifications will consolidate the leading position of MX in catalysis.

A physical “graph reservoir” is implemented using a metal cell at the diagonal-crossbar array (mCBA) structure and dynamic self-rectifying memristors. Spatiotemporal correlation information is extracted from mCBA using a unique mapping method called “inverted encoding.” Spatial (image recognition), temporal (time series prediction), and spatiotemporal (attention-deficit/hyperactivity disorder (ADHD) classification) analysis are effectively performed based on the graph reservoir.

Abstract

Memristor-based physical reservoir computing (RC) is a robust framework for processing complex spatiotemporal data parallelly. However, conventional memristor-based reservoirs cannot capture the spatial relationship between the time-varying inputs due to the specific mapping scheme assigning one input signal to one memristor conductance. Here, a physical “graph reservoir” is introduced using a metal cell at the diagonal-crossbar array (mCBA) with dynamic self-rectifying memristors. Input and inverted input signals are applied to the word and bit lines of the mCBA, respectively, storing the correlation information between input signals in the memristors. In this way, the mCBA graph reservoirs can map the spatiotemporal correlation of the input data in a high-dimensional feature space. The high-dimensional mapping characteristics of the graph reservoir achieve notable results, including a normalized root-mean-square error of 0.09 in Mackey–Glass time series prediction, a 97.21% accuracy in MNIST recognition, and an 80.0% diagnostic accuracy in human connectome classification.

4 in. Cu(111) wafers with ≈95% crystallinity are achieved with the introduction of a temperature gradient on Cu films with designed texture. During the abnormal growth of Cu(111) grain across the whole Cu wafer, in-plane twin boundaries are eliminated via the migration of out-of-plane grain boundaries. Graphene wafers grown on the resulting Cu(111) substrates exhibit improved crystallinity and electrical properties.

Abstract

Single-crystal graphene (SCG) wafers are needed to enable mass-electronics and optoelectronics owing to their excellent properties and compatibility with silicon-based technology. Controlled synthesis of high-quality SCG wafers can be done exploiting single-crystal Cu(111) substrates as epitaxial growth substrates recently. However, current Cu(111) films prepared by magnetron sputtering on single-crystal sapphire wafers still suffer from in-plane twin boundaries, which degrade the SCG chemical vapor deposition. Here, it is shown how to eliminate twin boundaries on Cu and achieve 4 in. Cu(111) wafers with ≈95% crystallinity. The introduction of a temperature gradient on Cu films with designed texture during annealing drives abnormal grain growth across the whole Cu wafer. In-plane twin boundaries are eliminated via migration of out-of-plane grain boundaries. SCG wafers grown on the resulting single-crystal Cu(111) substrates exhibit improved crystallinity with >97% aligned graphene domains. As-synthesized SCG wafers exhibit an average carrier mobility up to 7284 cm² V⁻¹ s⁻¹ at room temperature from 103 devices and a uniform sheet resistance with only 5% deviation in 4 in. region.

A novel, yet simple transfer printing process for the fabrication of biodegradable electronics is outlined in this study by using entirely biodegradable materials, aligning with eco-friendly principles. This process enables photolithography-based fabrication and transfer printing onto biodegradable polymer substrates, offering a versatile, pragmatic, and eco-friendly solution for diverse and sustainable biodegradable electronics.

Abstract

The biodegradable electronics are on the rise, not just due to their role in medical implants, but also because of their eco-friendly attributes. A variety of methods, including transfer printing, have been employed to integrate inorganic electronics onto biodegradable polymer substrates. However, the use of expensive materials, multiple intermediary steps, and labor-intensive procedures can undermine their environment-friendly benefits. Here, a straightforward yet efficient fabrication method is introduced for creating high-performance biodegradable electronic devices. This method leverages the controlled adhesion between the biodegradable device and substrate using self-assembled monolayers of octadecyltrichlorosilane. Mechanical and thermal analyses based on scratch tests and time-domain thermoreflectance quantify the adhesion by adjusting the packing density of octadecyltrichlorosilane. Controlled adhesion allows the photolithography process without delamination while facilitating easy delamination during transfer printing. The authors demonstrate the direct fabrication of electronics consisted of inorganic materials (Mg, Zn, SiO₂, Si nanomembrane) on wafers and transfer-printing onto polymer substrates via a single transfer step. This streamlined approach enables wafer-scale fabrication of biodegradable electronics, highlighting its potential for mass manufacturing. Pilot conceptual demonstration of mass-produced edible hydration sensors and their application in salivation measurement through in vivo model show the potential capability of proposed fabrication method in the use of practical level.

Hexagonal- and tetragonal-2H─PtSe₂ single-crystal flakes are controllably grown. It is found that the higher growth temperature would facilitate the nucleation of PtSe₂ with a-axis orientation, while c-axis PtSe₂ is preferred at lower temperatures. The single-crystal flakes are systematically studied by HRTEM, in situ high-pressure Raman, and polarization Raman. The electrical properties investigations demonstrate structure-correlated electronic and magnetic transport mechanisms.

Abstract

Due to the narrow bandgap, environment stability, and Pt vacancy-induced magnetism, PtSe₂ has been considered a promising candidate for future broadband photodetection and electronics. However, the growth of single-crystal PtSe₂ is still a challenge. Herein, the synthesis of hexagonal and tetragonal 2H─PtSe₂ single-crystal flakes by precisely tailoring the growth temperature is reported. Through atomic structure analysis, hexagonal and tetragonal flakes are proven c-axis and a-axis orientations of 2H─PtSe₂, indicating the preferred nucleation orientations are along the basal plane and vertically basal plane, respectively. The crystalline orientation-dependent properties are studied including high-pressure and polarized in situ-Raman, electrical transport. The out-of-basal plane vibration (A_1g) is sensitive to pressure showing 2.744 and 3.282 cm⁻¹ GPa⁻¹ corresponding to c-2H─PtSe₂ and a-2H─PtSe₂, respectively. The conductivity of c-2H─PtSe₂ is 57 times higher than that of a-2H─PtSe₂. Furthermore, by studying magnetic transport at low temperatures, both c-2H─PtSe₂ and a-2H─PtSe₂ exhibit butterfly-shaped magnetoresistance hysteresis suggesting their ferromagnetic property. The c-2H─PtSe₂ has a higher |MR| ratio and higher coercive field compared with a-2H─PtSe₂, indicating that across multilayer carrier regulation for c-2H─PtSe₂ is more difficult than intra-layer carrier regulation for a-2H─PtSe₂. This study opens the way to grow different crystalline orientations of 2D materials and will bring more abundant properties.

Soft climbing robots are developed based on a piezoelectric actuator and two bioinspired footpads with directional friction. The robots demonstrate versatile climbing on both smooth surfaces and rough surfaces. With intrinsic flexibility and efficient locomotion, the robots are demonstrated to deliver a cargo on transitional terrains. Scaled piezo-based robots are also demonstrated with increased traversal ability on inclined complex terrains.

Abstract

The ability to climb is crucial for terrestrial robots to expand their scope of application with improved navigation capacity. While some soft climbing devices are available, they often lack versatility when it comes to adapting to rough surfaces and changes in terrains. In this regard, a piezo-based soft robot with bioinspired footpads has been developed that can deliver superior climbing performance. Through their unprecedented directional friction, these footpads enable the robot to complete rigorous climbing tasks on surfaces with a climbing angle of 0–180° and a variety of roughness from ultra-smooth to millimeter-scale. With a unique slide-swing gait, the robot is able to complete fast climbing on a 90° substrate at a speed of 1.4 body lengths per second (BL/s) and self-transitional climbing on surfaces with a roughness difference of 11 µm and an angle change of 60° in 5 s without active control. A scaled down version of this climber is also presented with increased mobility to traverse steps of 3 body heights and slits of 0.75 BH effectively. In summary, the development of this soft robot with highly directional footpads paves the way for soft robots to navigate varied surfaces and ascend challenging terrains with improved mobility.

Owing to their outstanding photoluminescent properties, lanthanide-doped fluoride nanoparticles such as Eu³⁺ or Tb³⁺ doped CaF₂ and LaF₃ nanoparticles hold huge promise in bioimaging. Herein, these nanoparticles are used for the first time as bimodal fluorescent-Raman probes, thanks to their functionalization by Raman tags using diazonium salts. The resulting bimodal nanoprobes offer unprecedented opportunities for intracellular fluorescence and Raman imaging.

Abstract

The design of dual-mode fluorescence and Raman tags stimulates a growing interest in biomedical imaging and sensing applications as they offer the possibility to synergistically combine the versatility and velocity of fluorescence imaging with the specificity of Raman spectroscopy. Although lanthanide-doped fluoride nanoparticles (NPs) are among the most studied fluorescent nanoprobes, their use for the development of bimodal fluorescent-Raman probes has never been reported yet, to the best of the authors knowledge, probably due to the difficulty to functionalize them with Raman reporter groups. This gap is filled herein by proposing a fast and straightforward approach based on aryl diazonium salt chemistry to functionalize Eu³⁺ or Tb³⁺ doped CaF₂ and LaF₃ NPs by Raman scatters. The resulting surface-enhanced Raman spectroscopy (SERS)-encoded lanthanide-doped fluoride NPs retain their fluorescence labeling capacity and display efficient SERS activity for cell bioimaging. The potential of this new generation of bimodal nanoprobes is assessed through cell viability assays and intracellular fluorescence and Raman imaging, opening up unprecedented opportunities for biomedical applications.

Nature Synthesis, Published online: 23 October 2023; doi:10.1038/s44160-023-00422-3

Synthesizing phase-pure, higher-quantum-well thickness (n) 2D halide perovskites is challenging. Now, a general method, termed kinetically controlled space confinement, to synthesize 2D perovskites is reported. Transformation from low n-values to high n-values is achieved by tuning the temperature or time of crystallization.

Nature Communications, Published online: 23 October 2023; doi:10.1038/s41467-023-42447-4

The authors study Josephson junctions where the superconductors are Fe(Te,Se) flakes and the weak link is just a 0.36 nm van-der-Waals gap between the two stacked flakes. They report global device-level transport signatures of interfacial ferromagnetism.

Nature Communications, Published online: 24 October 2023; doi:10.1038/s41467-023-42567-x

van der Waals materials are usually characterized by a significant out-of-plane optical anisotropy, but in-plane birefringence is also necessary for photonics applications. Here, the authors report the presence of broadband optical anisotropy in a layered material, Ta2NiS5, showing in-plane birefringence of ~2 and ~0.5 in the visible and mid-infrared range, respectively.

Sustainability and human health risk are important factors to be considered in developing next-generation device technology. A materials screening protocol that brings in sustainability and safety considerations is proposed. Using ultrawide bandgap 2D materials as a backdrop, 25 candidates comprising only of low-risks elements are identified. Their potential in gate dielectric, power electronics, and ultraviolet photonics applications are demonstrated.

Abstract

The sustainable development of next-generation device technology is paramount in the face of climate change and the looming energy crisis. Tremendous effort is made in the discovery and design of nanomaterials that achieve device-level sustainability, where high performance and low operational energy cost are prioritized. However, many of such materials are composed of elements that are under threat of depletion and pose elevated risks to the environment and human health. The role of materials-level sustainability in computational screening efforts is overlooked thus far. This work presents a general van der Waals materials screening framework imbued with sustainability-motivated search criteria. Using ultrawide bandgap (UWBG) materials as a backdrop, 25 sustainable UWBG layered materials comprising only of low-risks elements result from this screening effort, with several meeting the requirements for dielectric, power electronics, and ultraviolet device applications. These findings constitute a critical first-step toward reinventing a more sustainable electronics landscape beyond silicon, with the framework established in this work serving as a harbinger of sustainable 2D materials discovery.

Owing to the atomic thickness, memristors based on 2D semiconductors show a high off-state current, which leads to additional power consumption. This work designs a versatile device structure to achieve an ultralow off-state current in α-In₂Se₃ memristors by incorporating a thin h-BN interlayer. It also realizes 32 distinct resistance states, enabling robust multi-bit memory capabilities.

Abstract

Memristors based on 2D semiconductors hold great promise due to their atomic-level thickness and tunable optoelectronic properties. However, a significant challenge lies in suppressing the large off-state current, which leads to additional standby power consumption. Here, a simple and versatile method is presented to address this issue by introducing a thin h-BN interlayer between 2D semiconductors and the electrodes. The thickness of the h-BN interlayer serves as a pivotal parameter for modulating the interfacial Schottky barrier, thereby influencing the off-state current level. This fabricated graphene/α-In₂Se₃/h-BN/Cr-Au memristor, forming a van der Waals heterostructure, exhibits unipolar resistive switching behavior. Remarkably, the memristor incorporating an 8 nm h-BN interlayer showcases an ultralow off-state current of 4.2 × 10⁻¹³ A, five orders of magnitude lower than that without the h-BN interlayer. It also achieves a current switching on/off ratio of up to 10⁹ and realizes 32 distinct resistance states, enabling robust multi-bit memory capabilities. Excellent stability and durability are maintained due to the self-encapsulation of the h-BN interlayer. Furthermore, this method is also applicable to memristors built on HfS₂, WS₂, and WSe₂, highlighting its broad potential for technological applications.