Jing Zhang

2D Cs₂AgIn _x Bi_{1- x} Cl₆ (0 ≤ x ≤ 1) alloyed double perovskite nanoplatelets are synthesized. The outstanding optical properties can be well explained by temperature-dependent photoluminescence spectroscopy study and first-principal density functional theory calculations. The as-prepared alloyed double perovskite nanoplatelets exhibit unprecedent stability toward air and polar solvents. All-solution-processed light-emitting diodes using this material as the sole emitting layer are successfully fabricated.

Abstract

Lead-free double perovskites have emerged as a promising class of materials with potential to be integrated into a wide range of optical and optoelectronic applications. Herein, the first synthesis of 2D Cs₂AgIn _x Bi_{1- x} Cl₆ (0 ≤ x ≤ 1) alloyed double perovskite nanoplatelets (NPLs) with well controlled morphology and composition is demonstrated. The obtained NPLs show unique optical properties with the highest photoluminescence quantum yield of 40.1%. Both temperature dependent spectroscopic studies and density functional theory calculation results reveal that the morphological dimension reduction and In–Bi alloying effect together boost the radiative pathway of the self-trapped excitons of the alloyed double perovskite NPLs. Moreover, the NPLs exhibit good stability under ambient conditions and against polar solvents, which is ideal for all solution-processing of the materials in low-cost device manufacturing. The first solution-processed light-emitting diodes is demonstrated using the Cs₂AgIn_0.9Bi_0.1Cl₆ alloyed double perovskite NPLs as the sole emitting component, showing luminance maximum of 58 cd m⁻² and peak current efficiency of 0.013 cd A⁻¹. This study sheds light on morphological control and composition-property relationships of double perovskite nanocrystals, paving the way toward ultimate utilizations of lead-free perovskite materials in diverse sets of real-life applications.

In films of the canonical antiferroelectric PbZrO₃, decreasing oxygen pressure during film deposition causes “ferroelectric-like” polarization switching (although the films retain the antiferroelectric orthorhombic phase). This is correlated with low-pressure bombardment-induced point-defect complexes that pin the antiferroelectric–ferroelectric phase-transition boundaries. In turn, by controlling the concentration of defect complexes, the dielectric tunability of PbZrO₃ can be adjusted.

Abstract

Antiferroelectrics, which undergo a field-induced phase transition to ferroelectric order that manifests as double-hysteresis polarization switching, exhibit great potential for dielectric, electromechanical, and electrothermal applications. Compared to their ferroelectric cousins, however, considerably fewer efforts have been made to understand and control antiferroelectrics. Here, it is demonstrated that the polarization switching behavior of an antiferroelectric can be strongly influenced and effectively regulated by point defects. In films of the canonical antiferroelectric PbZrO₃, decreasing oxygen pressure during deposition (and thus increasing adatom kinetic energy) causes unexpected “ferroelectric-like” polarization switching although the films remain in the expected antiferroelectric orthorhombic phase. This “ferroelectric-like” switching is correlated with the creation of bombardment-induced point-defect complexes which pin the antiferroelectric–ferroelectric phase boundaries, and thus effectively delay the phase transition under changing field. The effective pinning energy is extracted via temperature-dependent switching-kinetics studies. In turn, by controlling the concentration of defect complexes, the dielectric tunability of the PbZrO₃ can be adjusted, including being able to convert between “positive” and “negative” tunability near zero field. This work reveals the important role and strong capability of defects to engineer antiferroelectrics for new performance and functionalities.

Nature Electronics, Published online: 16 March 2023; doi:10.1038/s41928-023-00936-w

Magnetic meta-atoms made from lanthanum-doped barium hexaferrite can be used to create self-biased non-reciprocal metasurfaces capable of unidirectional transmission, non-reciprocal beam steering, non-reciprocal beam focusing and non-reciprocal holography.

Nature, Published online: 15 March 2023; doi:10.1038/s41586-023-05800-7

A Kondo lattice was realized in AB-stacked MoTe2/WSe2 moiré bilayers and widely and continuously gate-tunable Kondo temperatures were demonstrated.

Nature Physics, Published online: 16 March 2023; doi:10.1038/s41567-023-01947-2

Controlling the spatial distribution of optically active spin defects in solids is a long-standing goal in the quantum sensing and simulation communities. Measurements of the many-body noise generated by the spins were used to verify that a highly coherent and strongly interacting quantum spin system was confined to two dimensions within a diamond substrate.

Nature Materials, Published online: 14 March 2023; doi:10.1038/s41563-023-01526-z

Author Correction: Asymmetric magnetic proximity interactions in MoSe₂/CrBr₃ van der Waals heterostructures

Nature Materials, Published online: 16 March 2023; doi:10.1038/s41563-023-01494-4

Tip-induced excitonic luminescence nanoscopy of an atomically resolved van der Waals heterostructure.

Nature Communications, Published online: 16 March 2023; doi:10.1038/s41467-023-37197-2

Previous demonstrations of quantum interference in solids have mainly been limited to intra-layer transport within single conductors. Zhu et al. report a new type of inter-layer quantum interference in graphene-based double-layer devices, due to interference between carrier diffusion paths across the constituent layers.

A plasma-enhanced chemical vapor deposition method is developed to construct the 2D room-temperature magnetic MnGa₄-H crystal. Hydrogen insertion inside the MnGa₄ lattice can modulate the atomic distance and charge state, thereby ferrimagnetism can be achieved without destroying the structural configuration. 2D MnGa₄-H is high-quality and air-stable, demonstrating robust and stable room-temperature magnetism with a high Curie temperature above 620 K.

Abstract

2D room-temperature magnetic materials are of great importance in future spintronic devices while only very few are reported. Herein, a plasma-enhanced chemical vapor deposition approach is exploited to construct the 2D room-temperature magnetic MnGa₄-H single crystal with a thickness down to 2.2 nm. The employment of H₂ plasma makes hydrogen atoms can be easily inserted into the MnGa₄ lattice to modulate the atomic distance and charge state, thereby ferrimagnetism can be achieved without destroying the structural configuration. The as-obtained 2D MnGa₄-H crystal is high-quality, air-stable, and thermo-stable, demonstrating robust and stable room-temperature magnetism with a high Curie temperature above 620 K. This work enriches the 2D room-temperature magnetic family and opens up the possibility for the development of spintronic devices based on 2D magnetic alloys.

Nonlinear Hall Effect

As the heart and with the tremendous applications of terahertz technology, photodetectors suffer from considerable drawbacks imposed by weak optical absorption, and inefficient charge-separation mechanisms. In article number 2209557, Antonio Politano, Lin Wang, and co-workers report the nonlinear Hall effect operating at terahertz frequencies within strong spin-polarized topological states in CoTe₂ without invoking any semiconductor junctions or bias voltage, opening up fascinating route toward quantum wavefunction engineering.

Through systematically studying the crystallographic information of nitrides/2D materials interface, it is found that graphene is the ideal buffer layer for nitrides’ remote epitaxy while WS₂ for nitrides’ van der Waals epitaxy. As a result, a suitable growth-front construction strategies and basic guidelines for high-quality 2D-materials-assisted nitrides’ epitaxy is presented. This work may open a pathway toward various semiconductors heterointegration.

Abstract

Beyond traditional heteroepitaxy, 2D-materials-assisted epitaxy opens opportunities to revolutionize future material integration methods. However, basic principles in 2D-material-assisted nitrides’ epitaxy remain unclear, which impedes understanding the essence, thus hindering its progress. Here, the crystallographic information of nitrides/2D material interface is theoretically established, which is further confirmed experimentally. It is found that the atomic interaction at the nitrides/2D material interface is related to the nature of underlying substrates. For single-crystalline substrates, the heterointerface behaves like a covalent one and the epilayer inherits the substrate's lattice. Meanwhile, for amorphous substrates, the heterointerface tends to be a van der Waals one and strongly relies on the properties of 2D materials. Therefore, modulated by graphene, the nitrides’ epilayer is polycrystalline. In contrast, single-crystalline GaN films are successfully achieved on WS₂. These results provide a suitable growth-front construction strategy for high-quality 2D-material-assisted nitrides’ epitaxy. It also opens a pathway toward various semiconductors heterointegration.

Superlattices represent the epitome of combinatorial materials science: their properties can transcend those of their constituent layers, such as improved mobility with modulation doped structures. Here superlattice combinations are expanded into the morphological domain by introducing direct growth of alternating amorphous and polycrystalline layers, realizing a high-quality, high mobility “heteromorphic superlattice,” originally conceived by Raphael Tsu in 1989.

Abstract

An unconventional “heteromorphic” superlattice (HSL) is realized, comprised of repeated layers of different materials with differing morphologies: semiconducting pc-In₂O₃ layers interleaved with insulating a-MoO₃ layers. Originally proposed by Tsu in 1989, yet never fully realized, the high quality of the HSL heterostructure demonstrated here validates the intuition of Tsu, whereby the flexibility of the bond angle in the amorphous phase and the passivation effect of the oxide at interfacial bonds serve to create smooth, high-mobility interfaces. The alternating amorphous layers prevent strain accumulation in the polycrystalline layers while suppressing defect propagation across the HSL. For the HSL with 7:7 nm layer thickness, the observed electron mobility of 71 cm² Vs^-1, matches that of the highest quality In₂O₃ thin films. The atomic structure and electronic properties of crystalline In₂O₃/amorphous MoO₃ interfaces are verified using ab-initio molecular dynamics simulations and hybrid functional calculations. This work generalizes the superlattice concept to an entirely new paradigm of morphological combinations.

The superconducting transition temperature is greatly enhanced to be as large as 7.5 K in bulk Mo_{1− x} Ta _x Te₂ single crystals, which is attributed to an enrichment of density of states at the Fermi level. We also find the enhanced upper critical field beyond the Pauli limit in Ta-doped Weyl semimetal T _d-MoTe₂, which is likely due to the mixed singlet–triplet superconductivity.

Abstract

2D transition metal dichalcogenides are promising platforms for next-generation electronics and spintronics. The layered Weyl semimetal (W,Mo)Te₂ series features structural phase transition, nonsaturated magnetoresistance, superconductivity, and exotic topological physics. However, the superconducting critical temperature of the bulk (W,Mo)Te₂ remains ultralow without applying a high pressure. Here, the significantly enhanced superconductivity is observed with a transition temperature as large as about 7.5 K in bulk Mo_{1− x} Ta _x Te₂ single crystals upon Ta doping (0 ≤ x ≤ 0.22), which is attributed to an enrichment of density of states at the Fermi level. In addition, an enhanced perpendicular upper critical field of 14.5 T exceeding the Pauli limit is also observed in T _d-phase Mo_{1− x} Ta _x Te₂ (x = 0.08), indicating the possible emergence of unconventional mixed singlet–triplet superconductivity owing to the inversion symmetry breaking. This work provides a new pathway for exploring the exotic superconductivity and topological physics in transition metal dichalcogenides.

Nature Materials, Published online: 09 March 2023; doi:10.1038/s41563-023-01502-7

Large-size single-crystal van der Waals layered Bi2SeO5 has been synthesized with a high dielectric constant and high breakdown field strength for two-dimensional electronics applications.

Nature Physics, Published online: 09 March 2023; doi:10.1038/s41567-023-01983-y

Materials that simultaneously display ferroelectricity and magnetism, and are metallic, are very rare. Now, the two-dimensional electron gas in an oxide heterostructure brings all of this behaviour together.

Nature Electronics, Published online: 06 March 2023; doi:10.1038/s41928-023-00931-1

Magnetic hysteresis in multiferroic heterostructures formed from the two-dimensional magnetic insulator chromium germanium telluride and a thin ferroelectric polymer can be electrically controlled with voltages of around 5 V.

Wafer-scale tellurene is synthesized under room temperature by exploiting pulsed-laser deposition. On this basis, tellurene-based photodetector arrays are constructed, manifesting outstanding photosensitivity with the optimal responsivity, external quantum efficiency, and detectivity of 2.7 × 10⁷ A W⁻¹, 8.2 × 10⁹%, and 4.5 × 10¹⁵ Jones. Moreover, proof-of-concept ultrabroadband optical imaging is realized.

Abstract

High-resolution imaging is at the heart of the revolutionary breakthroughs of intelligent technologies, and it is established as an important approach toward high-sensitivity information extraction/storage. However, due to the incompatibility between non-silicon optoelectronic materials and traditional integrated circuits as well as the lack of competent photosensitive semiconductors in the infrared region, the development of ultrabroadband imaging is severely impeded. Herein, the monolithic integration of wafer-scale tellurene photoelectric functional units by exploiting room-temperature pulsed-laser deposition is realized. Taking advantage of the surface plasmon polaritons of tellurene, which results in the thermal perturbation promoted exciton separation, in situ formation of out-of-plane homojunction and negative expansion promoted carrier transport, as well as the band bending promoted electron–hole pair separation enabled by the unique interconnected nanostrip morphology, the tellurene photodetectors demonstrate wide-spectrum photoresponse from 370.6 to 2240 nm and unprecedented photosensitivity with the optimized responsivity, external quantum efficiency and detectivity of 2.7 × 10⁷ A W⁻¹, 8.2 × 10⁹% and 4.5 × 10¹⁵ Jones. An ultrabroadband imager is demonstrated and high-resolution photoelectric imaging is realized. The proof-of-concept wafer-scale tellurene-based ultrabroadband photoelectric imaging system depicts a fascinating paradigm for the development of an advanced 2D imaging platform toward next-generation intelligent equipment.

Quantum dots (QDs) are used as promising materials for next-generation displays due to their excellent electrical/optical properties. Strategies for patterning QDs via photolithography (conventional photolithography, lift off process, and direct photolithography) are comprehensively reviewed. This review also discusses the prospects for patterned QDs in terms of their structural and physical properties.

Abstract

Pixelating patterns of red, green, and blue quantum dots (QDs) is a critical challenge for realizing high-end displays with bright and vivid images for virtual, augmented, and mixed reality. Since QDs must be processed from a solution, their patterning process is completely different from the conventional techniques used in the organic light-emitting diode and liquid crystal display industries. Although innovative QD patterning technologies are being developed, photopatterning based on the light-induced chemical conversion of QD films is considered one of the most promising methods for forming micrometer-scale QD patterns that satisfy the precision and fidelity required for commercialization. Moreover, the practical impact will be significant as it directly exploits mature photolithography technologies and facilities that are widely available in the semiconductor industry. This article reviews recent progress in the effort to form QD patterns via photolithography. The review begins with a general description of the photolithography process. Subsequently, different types of photolithographical methods applicable to QD patterning are introduced, followed by recent achievements using these methods in forming high-resolution QD patterns. The paper also discusses prospects for future research directions.

The discovery of van der Waals magnets has provided a new platform for the electrical control of magnetism. Here, the realization of nonvolatile control of exchange bias and coercive fields in Fe₃GeTe₂/MgO heterostructures, and the gate voltage is as low as tens of mV which is two orders of magnitude smaller than those in previous experiments is presented.

Abstract

The discovery of van der Waals magnets has provided a new platform for the electrical control of magnetism. Recent experiments have demonstrated that the magnetic properties of van der Waals magnets can be tuned by various gate modulations, although most of them are volatile and require gate voltages no lower than several volts. Here, the realization of nonvolatile control of exchange bias and coercive fields in Fe₃GeTe₂/MgO heterostructures, and the gate voltage is as low as tens of mV which is two orders of magnitude smaller than those in previous experiments is presented. The discovery of an ionic-irradiated phase formed in Fe₃GeTe₂ by MgO sputtering revealed that an exchange bias effect can be obtained in this heterostructure and tuned from ≈700 to 0 Oe through voltages ranging from 5 to 20 mV. Owing to the high stability of oxidized Fe₃GeTe₂, the voltage-driven oxygen incorporated into Fe₃GeTe₂ from the irradiated phase induces a nonvolatile magnetism modulation that can be retained after turning off the gate voltage. These findings demonstrate a methodology to modulate the magnetism of van der Waals magnets, opening new opportunities to fabricate all-solid, long-retention, and low-dissipation nano-electronic devices using van der Waals materials.

Bimetal-incorporated black phosphorene (BP) structures are fabricated by a facile in situ electro-exfoliation/insertion method for efficient water splitting electrocatalysis. Bimetals (e.g., NiFe, NiPd) are of cationic and covalent incorporation with electron-deficient state in few-layer BP, presenting the excellent and anti-reconstruction catalytic performances in hydrogen evolution and oxygen evolution reactions in 1 m KOH electrolytes.

Abstract

Surface reconstruction (SRC) is a common phenomenon and a promotion manner for Ni/Co-based precatalysts during the water splitting process. However, the catalytic surface reconstruction will in turn complicate the streamlined prediction and modeling on the catalytic activity. Hence, the rational design of anti-SRC catalysts is highly desirable, but challengeable. In this article, a series of affordable bimetal-incorporated black phosphorene (BP) catalysts are constructed by an in situ electro-exfoliation/insertion method for anti-SRC water electrolysis. It is found that the bimetals (e.g., NiFe, NiPd) are of cationic and covalent incorporation with electron-deficient state in few-layer BP. The optimized bimetal-BP structures present excellent and stable catalytic performances with low overpotentials in hydrogen evolution (HER, 53 mV, NiPd-BP) and oxygen evolution (OER, 268 mV, NiFe-BP) reactions at 10 mA cm⁻² in 1 m KOH. The anti-SRC behaviors are elucidated by in situ Raman studies during HER/OER, probably due to the balanced electron transfer pathway on Ni sites. This research opens interesting possibilities for designing the anti-SRC catalysts for efficient hydrogen production and authentic structure-activity understandings.

Nature Nanotechnology, Published online: 06 March 2023; doi:10.1038/s41565-023-01335-0

Thickness-dependent photoluminescence quantum yield measurements in black phosphorus reveal a free-carrier to excitonic transition, differing from the behaviour of conventional semiconductors.

Nature Nanotechnology, Published online: 06 March 2023; doi:10.1038/s41565-023-01317-2

Wavefunctions in graphene artificial atoms reveal giant orbital magnetic moments.