Jiuxiang Dai

Nature Electronics, Published online: 19 June 2023; doi:10.1038/s41928-023-00982-4

A magnetic random-access memory device that has an antiferromagnetic material as its storage element can be electrically read using ferromagnetic tunnelling.

Nature Electronics, Published online: 19 June 2023; doi:10.1038/s41928-023-00980-6

Stacking a bilayer of chromium triiodide, a layered antiferromagnet, onto another with a twist angle gives rise to a moiré magnet with rich magnetic phases, including ferromagnetic and antiferromagnetic orders. The magnetic orders can be controlled through the twist angle, temperature and electrical gating, with the system also showing voltage-assisted magnetic switching.

Nature Electronics, Published online: 19 June 2023; doi:10.1038/s41928-023-00978-0

The magnetic state of twisted double bilayers of antiferromagnetic chromium triiodide can be controlled by electrical gating, twist angle and temperature.

Nature Photonics, Published online: 19 June 2023; doi:10.1038/s41566-023-01227-8

An integrated electro-optic isolator on thin-film lithium niobate enables non-reciprocal isolation by microwave-driven travelling-wave phase modulation. The isolator exhibits a maximum optical isolation of 48.0 dB at around 1,553 nm and an on-chip insertion loss of 0.5 dB.

Nature Nanotechnology, Published online: 19 June 2023; doi:10.1038/s41565-023-01414-2

In a simple two-probe device made of van der Waals dichalcogenide nano-flakes, two pathways are found to switch ferro-rotational domain states by application of a volt-scale voltage.

Nature Materials, Published online: 19 June 2023; doi:10.1038/s41563-023-01563-8

A two-dimensional conjugated polymer is synthesized that demonstrates low electron effective masses and high mobility. These properties show that this material could act as a viable alternative to silicon-based semiconductors.

Light: Science & Applications, Published online: 20 June 2023; doi:10.1038/s41377-023-01169-4

We organize integrated metasurfaces with conventional devices (LED, LC, MEMS, etc.), and their potential applications in VR/AR, LiDAR, and sensors.

The presented 2D metamaterial consists of two layers that are actuated separately by a remotely applied magnetic field. This novel bilayer design strategy enables the adjustment of the area density while simultaneously preserving the overall dimensions. These designs can be further exploited in acoustic applications, including highly tunable bandgaps and waveguides.

Abstract

2D metamaterials have immense potential in acoustics, optics, and electromagnetic applications due to their unique properties and ability to conform to curved substrates. Active metamaterials have attracted significant research attention because of their on-demand tunable properties and performances through shape reconfigurations. 2D active metamaterials often achieve active properties through internal structural deformations, which lead to changes in overall dimensions. This demands corresponding alterations of the conforming substrate, or the metamaterial fails to provide complete area coverage, which can be a significant limitation for their practical applications. To date, achieving area-preserving active 2D metamaterials with distinct shape reconfigurations remains a prominent challenge. In this paper, magneto-mechanical bilayer metamaterials are presented that demonstrate area density tunability with area-preserving capability. The bilayer metamaterials consist of two arrays of magnetic soft materials with distinct magnetization distributions. Under a magnetic field, each layer behaves differently, which allows the metamaterial to reconfigure its shape into multiple modes and to significantly tune its area density without changing its overall dimensions. The area-preserving multimodal shape reconfigurations are further exploited as active acoustic wave regulators to tune bandgaps and wave propagations. The bilayer approach thus provides a new concept for the design of area-preserving active metamaterials for broader applications.

The strategy of electrostatic force-induced deposition (EF-ID) is proposed by introducing alternating polyethyleneimine and fluorosilane patterns to synergistically improve the quantum dot (QD) pattern pixel accuracy, boost device transmittance, and reduce the device leakage current, which enables high resolution ranging from 1104 to 3031 PPI and a high efficiency of 15.6%, as well as highly transparent quantum dot light-emitting diodes (QLEDs) with a high transmittance of 90.7%, indicating an effective approach for high-resolution QLEDs with high efficiency and transparency.

Abstract

Aiming at next-generation displays, high-resolution quantum dot light-emitting diodes (QLEDs) with high efficiency and transparency are highly desired. However, there is limited study involving the improvements of QLED pixel resolution, efficiency, and transparency simultaneously, which undoubtedly restricts the practical applications of QLED for next-generation displays. Here, the strategy of electrostatic force-induced deposition (EF-ID) is proposed by introducing alternating polyethyleneimine (PEI) and fluorosilane patterns to synergistically improve the pixel accuracy and transmittance of QD patterns. More importantly, the leakage current induced by the void spaces between pixels that is usually reported for high-resolution QLEDs is greatly suppressed by substrate-assisted insulating fluorosilane patterns. Finally, high-performance QLEDs with high resolution ranging from 1104 to 3031 pixels per inch (PPI) and a high efficiency of 15.6% are achieved, among the best performances of high resolution QLEDs. Notably, the high resolution QD pixels greatly enhance the transmittance of the QD patterns, thus prompting an impressive transmittance of 90.7% for the transparent QLEDs (2116 PPI), which represents the highest transmittance of transparent QLED devices. Consequently, this work contributes an effective and general approach for high-resolution QLEDs with high efficiency and transparency.

CMOS-Compatible Te/Si photodetector is built by magnetron sputtering technology, in which the type II heterojunction constructed by Te and Si, the photogenerated carriers are effectively separated, which prolongs the carrier lifetime and improves the photoresponse by several orders of magnitude. The Te/Si heterojunction photodetector demonstrates excellent detectivity of 2.1 × 10¹³ Jones and fast turn-on time of 920 ns.

Abstract

High-quality photodetectors are always the main way to obtain external information, especially near-infrared sensors play an important role in remote sensing communication. However, due to the limitation of Silicon (Si) wide bandgap and the incompatibility of most near infrared photoelectric materials with traditional integrated circuits, the development of high performance and wide detection spectrum near infrared detectors suitable for miniaturization and integration is still facing many obstacles. Herein, the monolithic integration of large area tellurium optoelectronic functional units is realized by magnetron sputtering technology. Taking advantage of the type II heterojunction constructed by tellurium (Te) and silicon (Si), the photogenerated carriers are effectively separated, which prolongs the carrier lifetime and improves the photoresponse by several orders of magnitude. The tellurium/silicon (Te/Si) heterojunction photodetector demonstrates excellent detectivity and ultra-fast turn-on time. Importantly, an imaging array (20 × 20 pixels) based on the Te/Si heterojunction is demonstrated and high-contrast photoelectric imaging is realized. Because of the high contrast obtained by the Te/Si array, in comparison with the Si arrays, it significantly improve the efficiency and accuracy of the subsequent processing tasks when the electronic pictures are applied to artificial neural network (ANN) to simulate the artificial vision system.

CpG delivery nanoplatforms by MoS₂ nanosheets are developed to boost antitumor immunity in head and neck squamous cell carcinoma (HNSCC). Functionalized nanosheets with medium size and low PEI_0.8k coverage exhibit high CpG loading capacity and low cytotoxicity. The combination of nanoplatforms with anti-programmed death 1 dispalys excellent antitumor effect, which calls forth an efficient strategy for HNSCC treatment.

Abstract

Despite the promising achievements of immune checkpoint blockade (ICB) therapy for tumor treatment, its therapeutic effect against solid tumors is limited due to the suppressed tumor immune microenvironment (TIME). Herein, a series of polyethyleneimine (Mw = 0.8k, PEI_0.8k)-covered MoS₂ nanosheets with different sizes and charge densities are synthesized, and the CpG, a toll-like receptor-9 agonist, is enveloped to construct nanoplatforms for the treatment of head and neck squamous cell carcinoma (HNSCC). It is proved that functionalized nanosheets with medium size display similar CpG loading capacity regardless of low or high PEI_0.8k coverage owing to the flexibility and crimpability of 2D backbone. CpG-loaded nanosheets with medium size and low charge density (CpG@M _M-P _L) could promote the maturation, antigen-presenting capacity, and proinflammatory cytokines generation of bone marrow-derived dendritic cells (DCs). Further analysis reveals that CpG@M _M-P _L effectively boosts the TIME of HNSCC in vivo including DC maturation and cytotoxic T lymphocyte infiltration. Most importantly, the combination of CpG@M _M-P _L and ICB agents anti-programmed death 1 hugely improves the tumor therapeutic effect, inspiring more attempts for cancer immunotherapy. In addition, this work uncovers a pivotal feature of the 2D sheet-like materials in nanomedicine development, which should be considered for the design of future nanosheet-based therapeutic nanoplatforms.

The study explores chalcogen-rich 2D transition-metal (TM)-chalcogenides' potential for phase-change memory. The focus is on the layered TM-chalcogenide NbTe₄, showing a lower melting point and higher crystallization temperature than traditional phase-change materials (PCMs) such as Ge₂Sb₂Te₅. Further device evaluation demonstrates that NbTe₄ is an excellent solution for current PCM issueslike poor thermal stability and the high Reset energy.

Abstract

2D van der Waals (vdW) transition metal di-chalcogenides (TMDs) have garnered significant attention in the nonvolatile memory field for their tunable electrical properties, scalability, and potential for phase engineering. However, their complex switching mechanism and complicated fabrication methods pose challenges for mass production. Sputtering is a promising technique for large-area 2D vdW TMD fabrication, but the high melting point (typically T _m > 1000 °C) of TMDs requires elevated temperatures for good crystallinity. This study focuses on the low-T _m 2D vdW TM tetra-chalcogenides and identifies NbTe₄ as a promising candidate with an ultra-low T _m of around 447 °C (onset temperature). As-grown NbTe₄ forms an amorphous phase upon deposition that can be crystallized by annealing at temperatures above 272 °C. The simultaneous presence of a low T _m and a high crystallization temperature T _c can resolve important issues facing current phase-change memory compounds, such as high Reset energies and poor thermal stability of the amorphous phase. Therefore, NbTe₄ holds great promise as a potential solution to these issues.

Data-class-specific all-optical transformations are achieved using a diffractive neural network that is designed by deep learning. Experimentally validated at different parts of the electromagnetic spectrum, including near-infrared and terahertz wavelengths, these class-specific diffractive optical processors provide a fast and energy-efficient method for image and data encryption, enhancing data security and privacy.

Abstract

Diffractive optical networks provide rich opportunities for visual computing tasks. Here, data-class-specific transformations that are all-optically performed between the input and output fields-of-view (FOVs) of a diffractive network are presented. The visual information of the objects is encoded into the amplitude (A), phase (P), or intensity (I) of the optical field at the input, which is all-optically processed by a data-class-specific diffractive network. At the output, an image sensor-array directly measures the transformed patterns, all-optically encrypted using the transformation matrices preassigned to different data classes, i.e., a separate matrix for each data class. The original input images can be recovered by applying the correct decryption key (the inverse transformation) corresponding to the matching data class, while applying any other key will lead to loss of information. All-optical class-specific transformations covering A → A, I → I, and P → I transformations using various image datasets are numerically demonstrated. The feasibility of this framework is also experimentally validated by fabricating class-specific I → I transformation diffractive networks and is successfully tested at different parts of the electromagnetic spectrum, i.e., 1550 nm and 0.75 mm wavelengths. Data-class-specific all-optical transformations provide a fast and energy-efficient method for image and data encryption, enhancing data security and privacy.

By using conventional 3D printing it is possible to fabricate nanostructured polymer surfaces by using similar approaches as those used in nanoimprint lithography. By 3D printing, a polymer on top of a structured template, accurate free-standing replicas can be obtained. It is demonstrated that a nanostructured hydrophilic polymer surface can be accurately replicated on another polymer rendering enhanced hydrophobicity.

Fused filament fabrication, commonly referred to as 3D printing, is an additive manufacturing method finding plenty of applications nowadays. In contrast, polymer nanopatterning by nanolithographic techniques plays an important role in obtaining functional surfaces and coatings for applications in different fields including micro- and nanoelectronics. In spite of their relevance, additive manufacturing and polymer nanolithography have not found yet a common niche to be developed. Although both approaches are oriented to achieve different types of objects, it is shown that the confluence of both technologies can be desirable and potentially convenient. Herein, it is demonstrated that by employing conventional 3D printing, it is possible to fabricate nanostructured polymer surfaces in a relatively simple way by using similar approaches as those used in nanoimprint lithography but without the need for clean room conditions. To do that, a printed-assisted nanoimprint lithography concept (3DPrANIL) has been tested for different types of polymer and silicon templates. It is demonstrated that a polymeric nanostructured hydrophilic template can be replicated accurately on another polymer rendering a nanostructured surface with enhanced hydrophobicity. The results support 3DPrANIL as novel method to obtain micro- and nanostructured surfaces with different functionalities like iridescence and hydrophobicity.

Publication date: September 2023

Source: Progress in Materials Science, Volume 138

Author(s): Maria Inês Silva, Evgenii Malitckii, Telmo G. Santos, Pedro Vilaça

Nature Synthesis, Published online: 16 June 2023; doi:10.1038/s44160-023-00339-x

Ammonia synthesis is one of the most important chemical processes as it sustains global food production, but it is a highly polluting and energy-intensive process. Here, the challenges of decarbonizing the process to synthesize green ammonia are discussed.

Nature, Published online: 16 June 2023; doi:10.1038/d41586-023-01978-y

Microchip entrepreneur and architect of Moore’s Law.

Nanoporous structure is created on MoS₂ and a 20-nm-thick Al₂O₃ is deposited. The non-planar Al₂O₃ on nanoporous MoS₂ is confirmed using transmission electron microscopy and scanning electron microscopy. The nanoporous MoS₂ with non-planar Al₂O₃ field-effect transistor-based biosensors exhibit excellent bio-sensing properties owing to electrostatic control provided by non-planar Al₂O₃.

Abstract

Field-effect transistors-based biosensors (bio-FETs) have been considered an important technology for label-free and ultrasensitive point-of-care diagnostics. However, practical applications using bio-FETs are limited due to the trade-off between sensing reliability and sensitivity. This study suggests a reliable and sensitive bio-FETs based on nanoporous molybdenum disulfide (MoS₂) channels encapsulated by a non-planar high-k aluminum oxide (Al₂O₃) dielectric layer. Nanoporous MoS₂ thin film is fabricated with an abundant edge area and periodically ordered nanopores via block copolymer lithography. The ultra-thin Al₂O₃ dielectric layer deposited along the nanoporous structure of the MoS₂ realizes effective electrostatic control of charged biomolecules over the MoS₂ channel. In addition, it plays important roles in not only enhancing the electrical performance of the nanoporous MoS₂ bio-FETs, that is, mobility, hysteresis, and subthreshold swing, but also achieving effective biomolecular immobilization on the device surface. The nanoporous MoS₂ channel structure surrounded by non-planar Al₂O₃ detects a prostate cancer biomarker with an ultra-low limit of detection of 1 fg mL⁻¹. Moreover, the excellent selectivity, high sensitivity, and clinical reliability of the nanoporous MoS₂ bio-FETs are also confirmed. The proposed device platform provides new insights and technical advances in the field of FETs based sensors for future point-of-care devices.

A non-volatile electrically reconfigurable 2 × 2 MZI integrated with a low-loss phase-change material Sb₂Se₃ encapsulated in Al₂O₃ layers is reported. The phase change is electrically actuated by a forward-biased silicon p-i-n diode. The switch extinction ratio is more than 20 dB. More than 10 000 reversible phase-change cycles and 6-bit multilevel switching states are achieved.

Abstract

Mach–Zehnder interferometers (MZIs) integrated with phase-change materials have attracted great interest due to their low power consumption and ultra-compact size, which are favored for reconfigurable photonic processors. However, they suffer from a low optical extinction ratio and limited switching cycles due to high material loss and poor reversible repeatability caused by material degradation. Here a non-volatile electrically reconfigurable 2 × 2 MZI integrated with a low-loss phase-change material Sb₂Se₃ encapsulated in Al₂O₃ layers is demonstrated. The phase change is electrically actuated by a forward-biased silicon p-i-n diode. The switch extinction ratio is more than 20 dB due to the low-loss Sb₂Se₃-based phase shifter. By dividing the Sb₂Se₃ patch into small sub-cells to restrict the material reflow, more than 10 000 reversible phase-change cycles and 6-bit multilevel switching states are achieved by programming the electrical pulses. Its non-volatility, high endurance, and fine-tuning capability makes the device promising in large-scale low-power reconfigurable photonic processors.

A high piezoelectric molecular ferroelectric 1-azabicyclo[3.2.1]octonium perrhenate ([3.2.1-abco]ReO₄) is precisely designed by the novel chemical design strategy of ring enlargement. Intriguingly, its polycrystalline pellet can show a piezoelectric coefficient d ₃₃ as large as 118 pC/N, larger than that of the parent 1-azabicyclo[2.2.1]heptanium perrhenate ([2.2.1–abch]ReO₄) and those of most polycrystalline or even single-crystal molecular ferroelectrics.

Abstract

Inorganic ferroelectrics have long dominated research and applications, taking advantage of high piezoelectric performance in bulk polycrystalline ceramic forms. Molecular ferroelectrics have attracted growing interest because of their environmental friendliness, easy processing, lightweight, and good biocompatibility, while realizing the considerable piezoelectricity in their bulk polycrystalline forms remains a great challenge. Herein, for the first time, through ring enlargement, a molecular ferroelectric 1-azabicyclo[3.2.1]octonium perrhenate ([3.2.1-abco]ReO₄) with a large piezoelectric coefficient d ₃₃ up to 118 pC/N in the polycrystalline pellet form is designed, which is higher than that of the parent 1-azabicyclo[2.2.1]heptanium perrhenate ([2.2.1–abch]ReO₄, 90 pC/N) and those of most molecular ferroelectrics in polycrystalline or even single crystal forms. The ring enlargement reduces the molecular strain for easier molecular deformation, which contributes to the higher piezoelectric response in [3.2.1-abco]ReO₄. This work opens up a new avenue for exploring high piezoelectric polycrystalline molecular ferroelectrics with great potential in piezoelectric applications.

2D ferromagnet is a good platform to investigate topological effects and spintronic devices. Herein, interface engineering and an in-plane current are used to modulate the magnetic properties of the nearly room-temperature 2D ferromagnet Fe₅GeTe₂. An artificial topology phenomenon is observed in the Fe₅GeTe₂/MnPS₃ heterostructure which is induced by the generation and annihilation of the magnetic domains.

Abstract

2D ferromagnet is a good platform to investigate topological effects and spintronic devices owing to its rich spin structures and excellent external-field tunability. The appearance of the topological Hall Effect (THE) is often regarded as an important sign of the generation of chiral spin textures, like magnetic vortexes or skyrmions. Here, interface engineering and an in-plane current are used to modulate the magnetic properties of the nearly room-temperature 2D ferromagnet Fe₅GeTe₂. An artificial topology phenomenon is observed in the Fe₅GeTe₂/MnPS₃ heterostructure by using both anomalous Hall Effect and reflective magnetic circular dichroism (RMCD) measurements. Through tuning the applied current and the RMCD laser wavelength, the amplitude of the humps and dips observed in the hysteresis loops can be modulated accordingly. Magnetic field-dependent hysteresis loops demonstrate that the observed artificial topological phenomena are induced by the generation and annihilation of the magnetic domains. This work provides an optical method for investigating the topological-like effects in magnetic structures and proposes an effective way to modulate the magnetic properties of magnetic materials, which is important for developing magnetic and spintronic devices in van der Waals magnetic materials.

Chameleon-inspired highly brilliant photonic crystals are prepared by non-close–assembling high refractive index ZnS–silica core–shell structured particles in commercial acrylates. Furthermore, five derived photonic superstructures with distinct optical properties are fabricated by co-assembly of ZnS–silica and silica particles, and particle-selective etching strategy. These photonic superstructures show potential applications in information encryption and fluorescence enhancement.

Abstract

Inspired by the brilliant and tunable structural colors based on the large refractive index contrast (Δn) and non-close-packing structures of chameleon skins, ZnS–silica photonic crystals (PCs) with highly saturated and adjustable colors are fabricated. Due to the large Δn and non-close-packing structure, ZnS–silica PCs show 1) intense reflectance (maximal: 90%), wide photonic bandgaps, and large peak areas, 2.6–7.6, 1.6, and 4.0 times higher than those of silica PCs, respectively; 2) tunable colors by simply adjusting the volume fraction of particles with the same size, more convenient than the conventional way of altering particle sizes; and 3) a relatively low threshold of PC's thickness (57 µm) possessing maximal reflectance compared to that (>200 µm) of the silica PCs. Benefiting from the core–shell structure of the particles, various derived photonic superstructures are fabricated by co-assembling ZnS–silica and silica particles into PCs or by selectively etching silica or ZnS of ZnS–silica/silica and ZnS–silica PCs. A new information encryption technique is developed based on the unique reversible “disorder–order” switch of water-responsive photonic superstructures. Additionally, ZnS–silica PCs are ideal candidates for enhancing fluorescence (approximately tenfold), approximately six times higher than that of silica PC.

0D/2D hybrid structures are considered functional materials with complementary advantages that may not be realized with a single component. Here, recent discoveries related to multicomponent hybrid materials are introduced. Research trends in electronic and optoelectronic devices based on hybrid heterogeneous materials are also highlighted and the issues to be solved from the perspective of the materials and devices are discussed.

Abstract

Atomically thin 2D transition metal dichalcogenides (TMDs) have recently been spotlighted for next-generation electronic and photoelectric device applications. TMD materials with high carrier mobility have superior electronic properties different from bulk semiconductor materials. 0D quantum dots (QDs) possess the ability to tune their bandgap by composition, diameter, and morphology, which allows for a control of their light absorbance and emission wavelength. However, QDs exhibit a low charge carrier mobility and the presence of surface trap states, making it difficult to apply them to electronic and optoelectronic devices. Accordingly, 0D/2D hybrid structures are considered as functional materials with complementary advantages that may not be realized with a single component. Such advantages allow them to be used as both transport and active layers in next-generation optoelectronic applications such as photodetectors, image sensors, solar cells, and light-emitting diodes. Here, recent discoveries related to multicomponent hybrid materials are highlighted. Research trends in electronic and optoelectronic devices based on hybrid heterogeneous materials are also introduced and the issues to be solved from the perspective of the materials and devices are discussed.