Jiuxiang Dai

A crown ether–assisted assembly of hafnium and zirconium halide cluster emitting units enables near-unity blue and green emission.

An ultra-large scale stitchless atomic force microscopy that enables the characterization of a maximum area of 1 × 1 mm² through the innovative integration of a compliant nano-manipulator. This approach enables the characterization of ultra-large scale samples with zero stitching error and high throughput, expanding the scanning area of conventional AFMs by two orders of magnitude.

Abstract

The atomic force microscopy (AFM) is an important tool capable of characterization, measurement, and manipulation at the nanoscale with a vertical resolution of less than 0.1 nm. However, the conventional AFMs' scanning range is around 100 µm, which limits their capability for processing cross-scale samples. In this study, it proposes a novel approach to overcome this limitation with an ultra-large scale stitchless AFM (ULSS-AFM) that allows for the high-throughput characterization of an area of up to 1 × 1 mm² through a synergistic integration with a compliant nano-manipulator (CNM). Specifically, the compact CNM provides planar motion with nanoscale precision and millimeter range for the sample, while the probe of the ULSS-AFM interacts with the sample. Experimental results show that the proposed ULSS-AFM performs effectively in different scanning ranges under various scanning modes, resolutions, and frequencies. Compared with the conventional AFMs, the approach enables high-throughput characterization of ultra-large scale samples without stitching or bow errors, expanding the scanning area of conventional AFMs by two orders of magnitude. This advancement opens up important avenues for cross-scale scientific research and industrial applications in nano- and microscale.

This study focuses on growth of two-dimensional SnS film via pulsed laser deposition and tuning gas sensing properties via metal nanoparticles (Pd, Ag, and Au) decoration. A significant enhancement is observed in NO₂ sensing of Ag-decorated SnS. While Pd-decorated SnS exhibits selectivity toward H₂, In-situ Kelvin probe force microscopy is used to aid the comprehension of sensing mechanism.

Abstract

This study employs novel growth methodologies and surface sensitization with metal nanoparticles to enhance and manipulate gas sensing behavior of two-dimensional (2D)SnS film. Growth of SnS films is optimized by varying substrate temperature and laser pulses during pulsed laser deposition (PLD). Thereafter, palladium (Pd), gold (Au), and silver (Ag) nanoparticles are decorated on as-grown film using gas-phase synthesis techniques. X-ray diffraction (XRD), Raman spectroscopy, and Field-emission scanning electron microscopy (FESEM) elucidate the growth evolution of SnS and the effect of nanoparticle decoration. X-ray photoelectron spectroscopy (XPS) analyses the chemical state and composition. Pristine SnS, Ag, and Au decorated SnS films are sensitive and selective toward NO₂ at room temperature (RT). Ag nanoparticle increases the response of pristine SnS from 48 to 138% toward 2 ppm NO_2, which indicates electronic and chemical sensitization effect of Ag. Pd decoration on SnS tunes its selectivity toward H₂ gas with a response of 55% toward 70 ppm H₂ and limit of detection (LOD) < 1 ppm. In situ Kelvin probe force microscopy (KPFM) maps the work function changes, revealing catalytic effect of Ag toward NO₂ in Ag-decorated SnS and direct charge transfer between Pd and SnS during H₂ exposure in Pd-decorated SnS.

This study presents a novel dual vision active pixel image sensor array utilizing two step grown large-area bilayer WS₂. The WS₂-based TFTs exhibited remarkable electrical and optoelectronic properties, including high mobility, I _on/I _off ratio, and responsivity to visible and near-infrared light. Utilizing light stencil projection, the sensor array demonstrated RGB and NIR image sensing capabilities, showcasing potential applications in day and night vision, pedestrian detection, artificial intelligence (AI), and security systems.

Abstract

Transition metal dichalcogenides (TMDs) are a promising candidate for developing advanced sensors, particularly for day and night vision systems in vehicles, drones, and security surveillance. While traditional systems rely on separate sensors for different lighting conditions, TMDs can absorb light across a broad-spectrum range. In this study, a dual vision active pixel image sensor array based on bilayer WS₂ phototransistors was implemented. The bilayer WS₂ film was synthesized using a combined process of radio-frequency sputtering and chemical vapor deposition. The WS₂-based thin-film transistors (TFTs) exhibit high average mobility, excellent I _on/I _off, and uniform electrical properties. The optoelectronic properties of the TFTs array exhibited consistent behavior and can detect visible to near-infrared light with the highest responsivity of 1821 A W⁻¹ (at a wavelength of 405 nm) owing to the photogating effect. Finally, red, green, blue, and near-infrared image sensing capabilities of active pixel image sensor array utilizing light stencil projection were demonstrated. The proposed image sensor array utilizing WS₂ phototransistors has the potential to revolutionize the field of vision sensing, which could lead to a range of new opportunities in various applications, including night vision, pedestrian detection, various surveillance, and security systems.

This review presents a comprehensive overview of recent progress on the modulation and enhancement strategies for the SHG response of 2DLMs. Then, the remaining challenges and outlooks toward further extending and realizing the practical multifunctional applications of 2DLMs in nonlinear on-chip integrated devices with SHG modulation and enhancement characteristics are discussed.

Abstract

Second harmonic generation (SHG) as an essential nonlinear optical effect, has gradually shifted its research trend toward the integration and miniaturization of photonic and optoelectronic on-chip devices in recent years. 2D layered materials (2DLMs) open up a new research paradigm of nonlinear optics due to their large second-order susceptibility, atomically thin structure, and perfect phase-matching. However, 2DLMs are facing a bottleneck of weak SHG conversion efficiency limit caused by short light–matter interaction lengths at a nanoscale. Moreover, advances in integrated on-chip SHG devices based on 2DLMs rely on the continuing development of novel strategies with tunable and efficient SHG responses. Here, this review provides a comprehensive overview of recent progress in exploring highly efficient and tunable SHG responses in 2DLMs. Various modulation and enhancement strategies for the SHG response of 2DLMs are extensively studied and systematically discussed, which can be classified into two categories: symmetry breaking and light-matter interaction enhancement. Moreover, remaining challenges and outlooks toward further extending and realizing the practical applications of 2DLMs in nonlinear on-chip integrated devices with SHG modulation and enhancement characteristics are discussed.

The 2D binary phosphides, SnP₃, and BiP, are fabricated by molecular beam epitaxy on Cu₂Sn and bismuthene, respectively. Scanning tunneling microscopy/spectroscopy, complemented with theoretical calculations, reveals the evolution processes and physical properties. Interface interactions determine the phase and domain size of as-grown 2D phosphides, providing tailored properties with atomic-level precision.

Abstract

Combinations of phosphorus with main group III, IV, and V elements are theoretically predicted to generate 2D binary phosphides with extraordinary properties and promising applications. However, experimental synthesis is significantly lacking. Here, a general approach for preparing 2D binary phosphides is reported using single crystalline surfaces containing the constituent element of target 2D materials as the substrate. To validate this, SnP₃ and BiP, representing typical 2D binary phosphides, are successfully synthesized on Cu₂Sn and bismuthene, respectively. Scanning tunneling microscopy imaging reveals a hexagonal pattern of SnP₃ on Cu₂Sn, while α-BiP can be epitaxially grown on the α-bismuthene domain on Cu₂Sb. First-principles calculations reveal that the formation of SnP₃ on Cu₂Sn is associated with strong interface bonding and significant charge transfer, while α-BiP interacts weakly with α-bismuthene so that its semiconducting property is preserved. The study demonstrates an attractive avenue for the atomic-scale growth of binary 2D materials via substrate phase engineering.

Multi-Modal Anti-Counterfeiting

In article number 2305469, Tong Zhang, Dan Su, and co-workers introduce a thermal-assisted non-planar nanostructure transfer printing technique for the multiscale patterning of polystyrene nanospheres. With a resolution exceeding 2750 pixels per inch, the multiscale colloidal nanostructure patterns on a 4-inch wafer yield diverse optical images when subjected to various light excitations. This cover artwork highlights multi-modal optical anti-counterfeiting enabled by structural patterns at hierarchical length scales.

Nanotransfer Printing

In article number 2303704, Jun-Ho Jeong, Yeon Sik Jung, Inkyu Park, and co-workers highlight recent advances and future aspects of nanotransfer printing (nTP) technologies. Based on the transfer mechanism, the advantages and challenges of various nTP processes are discussed. In addition, emerging applications of nTP technologies in the field of physical, optical, chemical, and electrochemical devices are also presented.

npj 2D Materials and Applications, Published online: 05 January 2024; doi:10.1038/s41699-023-00437-6

Electronic transport in graphene with out-of-plane disorder

Nature Physics, Published online: 05 January 2024; doi:10.1038/s41567-023-02291-1

Thermoelectric measurements show an unusual form of critical behaviour at the superconducting quantum phase transition in monolayer WTe2.

Two dimensional (2D) metastable-phase oxides, which combine the distinctive characteristics of metal oxides, 2D materials, and metastable-phase materials, have attracted significant attention. This Minireview predicts the occurrence and highlights the advantages, reliable syntheses, and catalytic applications of 2D metastable-phase oxides.

Abstract

Since the discovery of graphene, the development of new two-dimensional (2D) materials has received considerable interest. Recently, as a newly emerging member of the 2D family, 2D metastable-phase oxides that combine the unique advantages of metal oxides, 2D structures, and metastable-phase materials have shown enormous potential in various catalytic reactions. In this review, the potential of various 2D materials to form a metastable-phase is predicted. The advantages of 2D metastable-phase oxides for advanced applications, reliable methods of synthesizing 2D metastable-phase oxides, and the application of these oxides in different catalytic reactions are presented. Finally, the challenges associated with 2D metastable-phase oxides and future perspectives are discussed.

In this review, the high-throughput (HTP) strategies in the discovery of thermoelectric (TE) materials, including performance descriptor, HTP calculation, HTP experiment, and machine learning are systematically summarized. The applications and progress of the four HTP strategies in TEs are reviewed. In addition, the challenges and possible directions in future research are also discussed.

Abstract

Searching for new high-performance thermoelectric (TE) materials that are economical and environmentally friendly is an urgent task for TE society, but the advancements are greatly limited by the time-consuming and high cost of the traditional trial-and-error method. The significant progress achieved in the computing hardware, efficient computing methods, advance artificial intelligence algorithms, and rapidly growing material data have brought a paradigm shift in the investigation of TE materials. Many electrical and thermal performance descriptors are proposed and efficient high-throughput (HTP) calculation methods are developed with the purpose to quickly screen new potential TE materials from the material databases. Some HTP experiment methods are also developed which can increase the density of information obtained in a single experiment with less time and lower cost. In addition, machine learning (ML) methods are also introduced in thermoelectrics. In this review, the HTP strategies in the discovery of TE materials are systematically summarized. The applications of performance descriptor, HTP calculation, HTP experiment, and ML in the discovery of new TE materials are reviewed. In addition, the challenges and possible directions in future research are also discussed.

Arbitrary spectral engineering of optical microresonators is demonstrated in the anisotropic lithium niobate platform using gradient-design photonic crystal rings (PhCR), and a “mirror” is constructed in the synthetic frequency dimension based on an actively-modulated gradient-PhCR. This work opens up new paths toward arbitrary control of electro-optic comb spectral shapes and exploration of novel physics in the frequency degree of freedom.

Abstract

On-chip optical microresonators are essential building blocks in integrated optics. The ability to arbitrarily engineer their resonant frequencies is crucial for exploring novel physics in synthetic frequency dimensions and practical applications like nonlinear optical parametric processes and dispersion-engineered frequency comb generation. Photonic crystal ring (PhCR) resonators are a versatile tool for such arbitrary frequency engineering, by controllably creating mode splitting at selected resonances. To date, these PhCRs have mostly been demonstrated in isotropic photonic materials, while such engineering can be significantly more complicated in anisotropic platforms that often offer more fruitful optical properties. Here, the spectral engineering of chip-scale optical microresonators is realized in the anisotropic lithium niobate (LN) crystal by a gradient design that precisely compensates for variations in both refractive index and perturbation strength. Controllable frequency splitting is experimentally demonstrated at single and multiple selected resonances in LN PhCR resonators with different sizes, while maintaining high quality-factors up to 1 × 10⁶. Moreover, a sharp boundary is experimentally constructed in the synthetic frequency dimension based on an actively modulated x-cut LN gradient-PhCR, opening up new paths toward the arbitrary control of electro-optic comb spectral shapes and exploration of novel physics in the frequency degree of freedom.

Antiferromagnetic spintronics has gained remarkable development in recent years. In this Perspective, the latest research progress in this field is reviewed. It is emphasized that, distinct from ferromagnets, the richness in complex antiferromagnetic crystal structures is the unique and essential virtue of antiferromagnets that can endow them with exotic properties for spintronics.

Abstract

Antiferromagnets constitute promising contender materials for next-generation spintronic devices with superior stability, scalability, and dynamics. Nevertheless, the perception of well-established ferromagnetic spintronics underpinned by spontaneous magnetization seemed to indicate the inadequacy of antiferromagnets for spintronics—their compensated magnetization has been perceived to result in uncontrollable antiferromagnetic order and subtle magnetoelectronic responses. However, remarkable advancements have been achieved in antiferromagnetic spintronics in recent years, with consecutive unanticipated discoveries substantiating the feasibility of antiferromagnet-centered spintronic devices. It is emphasized that, distinct from ferromagnets, the richness in complex antiferromagnetic crystal structures is the unique and essential virtue of antiferromagnets that can open up their endless possibilities of novel phenomena and functionality for spintronics. In this Perspective, the recent progress in antiferromagnetic spintronics is reviewed, with a particular focus on that based on several kinds of antiferromagnets with special antiferromagnetic crystal structures. The latest developments in efficiently manipulating antiferromagnetic order, exploring novel antiferromagnetic physical responses, and demonstrating prototype antiferromagnetic spintronic devices are discussed. An outlook on future research directions is also provided. It is hoped that this Perspective can serve as guidance for readers who are interested in this field and encourage unprecedented studies on antiferromagnetic spintronic materials, phenomena, and devices.

This work proposes an effective mechanism for preparing the single-walled carbon nanotubes with high chirality using the solid Co catalyst, i.e., adjusting the experimental parameters to influence the carbon feeding rate to control the carbon gradient in NP to further restrain the structural fluctuation of the catalyst at the nucleation stage of catalytic growth of single-walled carbon nanotubes.

Abstract

Using solid nanoparticles (NPs) as catalysts is the most effective method to achieve catalytic growth of single-walled carbon nanotubes (SWCNTs) with ultrapure chirality. Until now, SWCNTs with a suitable chirality purity have not been prepared in experiments. That is, the evolution of solid NPs during the catalytic growth of SWCNTs is in contradiction with the original concept of a changeless structure. Hence, in this work, the evolution mechanism of solid cobalt NPs during the nucleation process of SWCNTs is analyzed through molecular dynamics. Similar to the experimental observations, the results show that a drastic structural fluctuation of the NPs occurs during the nucleation of SWCNTs. This structural fluctuation is caused by the fact that the elastic strain energy and surface energy of the NPs can be tuned when a carbon gradient exists between the subsurface and interior of the NP. Furthermore, such a carbon gradient can be reduced by changing the carbon feeding rate. This work not only reveals the evolution mechanism of solid catalysts during the nucleation of SWCNTs but also provides prospects for realizing solid catalysts with a changeless structure by tuning the experimental parameters.

Nature Electronics, Published online: 08 January 2024; doi:10.1038/s41928-023-01112-w

An inverter that uses a self-biased molybdenum disulfide homojunction as the load and n-type transistor as the driver can exhibit lower static power than complementary metal–oxide–semiconductor (CMOS) or pseudo-n-type metal–oxide–semiconductor (NMOS) architectures.

Nature Materials, Published online: 08 January 2024; doi:10.1038/s41563-023-01783-y

The local layer alignment in a wide range of trilayer graphene structures has been extracted by interferometric four-dimensional scanning transmission electron microscopy, uncovering the complex picture of lattice reconstruction in twisted trilayers.

Nature Materials, Published online: 08 January 2024; doi:10.1038/s41563-023-01788-7

The metal monochalcogenides are a group of van der Waals layered semiconductors with ultra-high plasticity. It is now revealed that their plasticity is attributed to the ability to transform their stacking order or phases, coupled with the concurrent generation of a micro-crack network.

Nature Materials, Published online: 08 January 2024; doi:10.1038/s41563-023-01734-7

Employing light-transformable polymers, multiple physical unclonable functions are demonstrated within a single device with all-optical reversible reconfigurability. Such devices may enable quantum secure authentication and nonlinear cryptographic key generation applications.

The novel confined interfacial chalcogenization (CIC) method to develop robust transition metal dichalcogenides (TMDs) possessing an ultraclean interface with a metal presents a promising alternative to conventional chemical vapor deposition (CVD). CIC-TMDs overcome limitations associated with CVD such as defects, doping impurities, and degradation, thus proving to be versatile for the development of memristors for electronic devices.

Abstract

Acquisition of defect-free transition metal dichalcogenides (TMDs) channels with clean heterojunctions is a critical issue in the production of TMD-based functional electronic devices. Conventional approaches have transferred TMD onto a target substrate, and then apply the typical device fabrication processes. Unfortunately, those processes cause physical and chemical defects in the TMD channels. Here, a novel synthetic process of TMD thin films, named confined interfacial chalcogenization (CIC) is proposed. In the proposed synthesis, a uniform TMDlayer is created at the Au/transition metal (TM) interface by diffusion of chalcogen through the upper Au layer and the reaction of chalcogen with the underlying TM. CIC allows for ultraclean heterojunctions with the metals, synthesis of various homo- and hetero-structured TMDs, and in situ TMD channel formation in the last stage of device fabrication. The mechanism of TMD growth is revealed by the TM-accelerated chalcogen diffusion, epitaxial growth of TMD on Au(111). We demonstrated a wafer-scale TMD-based vertical memristors which exhibit excellent statistical concordance in device performance enabled by the ultraclean heterojunctions and superior uniformity in thickness. CIC proposed in this study represents a breakthrough in in TMD-based electronic device fabrication and marking a substantial step toward practical next-generation integrated electronics.

For sake of practical application, an efficient surface defect restoring strategy via InCl₃-assist is developed to optimize the particle morphology and improve the luminescence properties of the blue-emitting lead-free Cs₂ZrCl₆ NCs for X-ray imaging and blue LED. Moreover, the restored type of the defects is clarified by combining comprehensive experimental and theoretical analysis.

Abstract

As one type of recent emerging lead-free perovskites, Cs₂ZrCl₆ nanocrystals are widely concerned, benefiting from the eminent designability, high X-ray cutoff efficiency, and favorable stability. Improving the luminescence performance of Cs₂ZrCl₆ nanocrystals has great importance to cater for practical applications. In view of the surface defects frequently formed by the liquid phase method, the particle morphology and surface quality of this material are expected to be regulated if certain intervention is made in the synthesis process. In the work, differing from normal cell lattice modulation based on the ion doping, the grain size and surface morphology of Cs₂ZrCl₆ nanocrystals are optimized via adding a certain amount of InCl₃ to the synthetic solution. The surface defects are restored to inhibit the defect-induced non-radiative transition, resulting in the improvement of the luminescence properties. Moreover, a flexible Cs₂ZrCl₆@polydimethylsiloxane film with excellent heat, water, and bending resistance and a light-emitting diode (LED) device are fabricated, exhibiting excellent application potential for X-ray imaging and blue LED.

This comprehensive review explores quantum dot (QD) patterning technologies for display applications, aimed at expediting the successful commercialization of QD light-emitting diodes (QD-LEDs). The article evaluates the current state and inherent potential of QD patterning techniques, including optical lithography, transfer printing, and inkjet printing. Moreover, this study introduces pioneering exploratory patterning techniques for QDs, thereby broadening the horizons of QD-LEDs for diverse applications.

Abstract

Colloidal quantum dots (QDs) are widely regarded as advanced emissive materials with significant potential for display applications owing to their excellent optical properties such as high color purity, near-unity photoluminescence quantum yield, and size-tunable emission color. Building upon these attractive attributes, QDs have successfully garnered attention in the display market as down-conversion luminophores and now venturing into the realm of self-emissive displays, exemplified by QD light-emitting diodes (QD-LEDs). However, despite these advancements, there remains a relatively limited body of research on QD patterning technologies, which are crucial prerequisites for the successful commercialization of QD-LEDs. Thus, in this review, an overview of the current status and prospects of QD patterning technologies to accelerate the commercialization of QD-LEDs is provided. Within this review, a comprehensive investigation of three prevailing patterning methods: optical lithography, transfer printing, and inkjet printing are conducted. Furthermore, several exploratory QD patterning techniques that offer distinct advantages are introduced. This study not only paves the way for successful commercialization but also extends the potential application of QD-LEDs into uncharted frontiers.

npj 2D Materials and Applications, Published online: 10 January 2024; doi:10.1038/s41699-023-00438-5

Raman scattering excitation in monolayers of semiconducting transition metal dichalcogenides