Jing Zhang

Nature Photonics, Published online: 08 May 2023; doi:10.1038/s41566-023-01207-y

We show perovskite X-ray detection at zero-voltage bias with operational device stability exceeding one year. Detection efficiency of 88% and noise-equivalent dose of 90 pGyair are obtained with 18 keV X-rays, allowing single-photon-sensitive, low-dose and energy-resolved X-ray imaging.

Nature Electronics, Published online: 08 May 2023; doi:10.1038/s41928-023-00965-5

A parallel in-memory wireless computing scheme that is based on memristive crossbar arrays can provide energy-efficient wireless data transmission using radio, acoustic and light waves.

Suffering from inefficient domain distribution management, the evolution of blue perovskite light-emitting diode (PeLEDs) is relatively backward. The characteristics of quasi-2D perovskites lead to the necessity of domain distribution management. Herein, a series of strategies, including cations with small radius, spacer cations, phosphine oxide additives, inorganic additives, solvent selection, and technological methods is detailed and summarized.

Abstract

Quasi-2D perovskites, as one of the promising materials applied in perovskite light-emitting diodes (PeLEDs), have attracted great attention for their superior semiconductor properties. The inherent multiquantum well structure can induce a strong confinement effect, which is especially suitable for blue emission. However, compared to their green counterparts, blue emitters constructed from quasi-2D perovskites are more sensitive to n domain distribution (where n represents the number of PbX₆ inorganic layers). Suffering from inefficient domain distribution management, blue PeLEDs now face a variety of negative issues, including color instability, multipeak emission, and poor fluorescence yield. In this review, the development of blue PeLEDs and the optical properties of quasi-2D perovskites are overviewed. Then, a classification and summary of strategies for domain distribution management are proposed. Finally, the challenges and potential directions of domain distribution management in quasi-2D perovskites are summarized. This review is expected to provide a comprehensive perspective and reference on domain distribution management toward efficient blue quasi-2D PeLEDs.

A self-powered LNO/BFO/ITO UV photodetector is constructed on flexible mica substrate by sol–gel method. The sensor exhibits enhanced photocurrent over a wide temperature range (33–130 °C) and outperforms bulk materials photocurrent. It provides favorable guidance for the further development and application of ferroelectric thin films.

Abstract

The current research on ferroelectric photovoltaic materials is concentrated on enhancing the output photocurrent. As solar cells operate at high temperatures, it is crucial to take into account the effect of increasing temperatures on ferroelectric photovoltaics. In this study, an LNO (lanthanum nickelate, LaNiO₃)/BFO (bismuth ferrate, BiFeO₃)/ITO (indium tin oxide) device is constructed on a mica substrate by sol–gel method. The device achieves output photocurrent enhancement at a wide temperature range (33–183 °C), with the largest photocurrent enhancement at 130 °C, which is 178% relative to room temperature, and the output power is also increased by 9.88 times. At the same time, compared with BFO bulk, it is found that the performance of BFO film is always higher than that of bulk in the test temperature range, and the output photocurrent of BFO film at room temperature is 104 times higher than that of bulk. This article investigates the effect of high temperatures on ferroelectric photovoltaics and also provides a strategy for enhancing the photovoltaic performance of ferroelectric films, providing guidance for future applications of ferroelectric films in flexible solar cells and other applications.

In d ⁰ magnetism, the delocalization nature enables strong coupling, i.e., exchange coupling and Dzyaloshinskii–Moriya interaction, and thereby the stability of skyrmions in a wide range of temperature. Meanwhile, the small magnetic moment d ⁰ renders skyrmions relatively robust in terms of perturbations raised by magnetic field.

Abstract

Magnetic skyrmions are topologically protected chiral spin textures that hold great promise for information storage and processing. The current research efforts on magnetic skyrmions are exclusively based on d-orbital magnetism, which restricts their existence in a narrow window of temperature-external magnetic field (T-B) phase diagram. Herein, employing first-principles and Monte-Carlo simulations, the work reports the identification of d ⁰ magnetic skyrmions in 2D lattice of Tl₂NO₂. Arising from inversion asymmetry and strong spin-orbit coupling compensated by ligand of heavy element, large Dzyaloshinskii–Moriya interaction is obtained in monolayer Tl₂NO₂. This, competed with p-orbital exchange interaction, leads to the d ⁰ skyrmion physics under external magnetic field. Importantly, different from d-orbital topological magnetism, the d ⁰ magnetic skyrmions can be stabilized in a wide window of T-B phase diagram. The underlying physics is related to the small magnetic moment and delocalization character of d ⁰ magnetism. Furthermore, the work also demonstrates that the d ⁰ magnetic skyrmions are strongly coupled with ferroelectricity. These findings open a new direction for magnetic skyrmion research.

Thermal Transistors

In article number 2214939, Hiromichi Ohta and co-workers demonstrate solid-state thermal transistors that control the thermal conductivity (κ) of strontium cobaltite by electrochemical redox treatment. Oxidized SrCoO₃ shows a higher κ of 3.8 W m⁻¹ K⁻¹ while reduced SrCoO₂ shows a lower κ of 0.95 W m⁻¹ K⁻¹. The on/off ratio is 4, and it plays like the shutter of heat flow.

Nature Nanotechnology, Published online: 08 May 2023; doi:10.1038/s41565-023-01386-3

The implementation of topological antiferromagnetic vortices in information storage devices requires an efficient method of nucleation and a way to control their movement. Here the authors find CuMnAs to be a suitable electrically conducting antiferromagnet host material for topological spin textures.

MoS₂ films are directly deposited on the diamond surface by atomic layer deposition (ALD) to achieve efficient energy transfer between MoS₂ films and nitrogen vacancy (NV) centers. By changing the number of ALD cycles, MoS₂ films with different thicknesses are obtained on the diamond surface, which further realizes the precise control of energy transfer between MoS₂ films and NV centers.

Abstract

Energy transfer between 2D MoS₂ films and fluorescent emitters is widely used in biological detection and imaging. In this paper, by regulating the thickness of the MoS₂ film on the diamond surface through the number of atomic layer deposition (ALD) cycles, the energy transfer efficiency between the nitrogen vacancy (NV) center and the MoS₂ film is improved and precisely controlled. When the number of ALD cycles is 8, the energy transfer efficiency between the 2D MoS₂ film and the NV center is 86.35%. Furthermore, when the number of ALD cycles is more significant than 140, compared with 2D and 3D graphene structures, the energy transfer efficiency of the NV center is increased by 126.55% and 24.60%, respectively. Meantime, the fluorescence lifetime of the NV center is reduced in the presence of the MoS₂ film, indicating that the MoS₂ film provides a new, additional fluorescence decay channel for the NV center in the MoS₂ film and the NV center system. Moreover, ALD can also effectively improve the tightness of the contact interface between the MoS₂ film and the diamond. This paper provides a new method and experimental basis for regulating the photon emission behavior of emitters.

The proposed synthesis methods of amorphous MXene are discussed. The unique structure of amorphous MXenes may possess unexpected properties. The work opens new perspectives on the possibility of MXene amorphization, and their energy conversion, energy storage, and other applications.

Abstract

Recently, novel amorphous nanomaterials formed by introducing atomic irregular arrangement factors have been successfully fabricated, showing superior performance in catalysis, energy storage, and mechanics. Among them, 2D amorphous nanomaterials are the stars, as they combine the benefits of both 2D structure and amorphous. Up to now, many research studies have been published on the study of 2D amorphous materials. However, as one of the most important parts of 2D materials, the research on MXenes mainly focuses on the crystalline counterpart, while the study of highly disordered forms is much less. This work will provide insight into the possibility of MXenes amorphization, and discusses the application prospect of amorphous MXenes materials.

The introduction of 2D silicene into bendable membranes allows investigating its optothermal and piezoresistive properties when external strain is applied on a micro and macroscale, thus representing an advance toward a new generation of flexible and fully silicon-based devices.

Abstract

Due to their superior mechanical properties, 2D materials have gained interest as active layers in flexible devices co-integrating electronic, photonic, and straintronic functions altogether. To this end, 2D bendable membranes compatible with the technological process standards and endowed with large-scale uniformity are highly desired. Here, it is reported on the realization of bendable membranes based on silicene layers (the 2D form of silicon) by means of a process in which the layers are fully detached from the native substrate and transferred onto arbitrary flexible substrates. The application of macroscopic mechanical deformations induces a strain-responsive behavior in the Raman spectrum of silicene. It is also shown that the membranes under elastic tension relaxation are prone to form microscale wrinkles displaying a local generation of strain in the silicene layer consistent with that observed under macroscopic mechanical deformation. Optothermal Raman spectroscopy measurements reveal a curvature-dependent heat dispersion in silicene wrinkles. Finally, as compelling evidence of the technological potential of the silicene membranes, it is demonstrated that they can be readily introduced into a lithographic process flow resulting in the definition of flexible device-ready architectures, a piezoresistor, and thus paving the way to a viable advance in a fully silicon-compatible technology framework.

A stable quasi-gradient (Cu-Cu₃Sn-Sn-SnO₂) 3D skeleton consisting of a Sn/SnO₂ layer metallurgically bonded to copper foam through Cu₃Sn alloy is designed in one-step by a nanosecond pulsed laser-assisted deposition strategy (LAD-SSC@CF). The Li₂₂Sn₅ lipophilic site created during the pre-lithiation process and porous space of 3D skeleton enable LAD-SSC@CF as an effective lithium host promoting homogeneous plating/stripping of lithium.

Abstract

The continuous growth of Li dendrites and volumetric deformation of Li severely impede the commercial application of Li metal anodes. To regulate Li stripping/plating, electrodeposition or magnetron sputtering is extensively utilized to fabricate lithiophilic-metal deposited 3D Li hosts. However, the binding force between lithiophilic-metal and host is weak, inevitably leading to numerous cracks/defects of lithiophilic-surface-layer during Li plating/stripping. Herein, a quasi-gradient (Cu-Cu₃Sn-Sn-SnO₂) 3D skeleton consisting of hierarchical Sn/SnO₂ composite metallurgically bonded to copper foam through Cu₃Sn alloy (LAD-SSC@CF) is designed, and prepared in one-step by a nanosecond-pulsed-laser-assisted deposition strategy. The homogeneous Li nucleation sites provided by Li₂₂Sn₅ formed by the reaction of Sn/SnO₂ with Li can inhibit Li dendrites growth. Meanwhile, the porous space and strong bonding of Cu₃Sn layer avoid structural deterioration of anodes. Consequently, a symmetric cell based on LAD-SSC@CF@Li exhibits an outstanding cycling stability of 1500 h at 1 mA cm⁻². In particular, a full cell with LiFePO₄ cathode provides good capacity retention of 81.3% at 5 C after 600 cycles. Moreover, the successful preparation of other composite materials (In, Zn, Sn-Bi, etc.) loading on various substrates (Kapton film, ceramic, copper foil, etc.) demonstrates the versatility of pulsed-laser-assisted deposition strategy for preparing battery materials.

Nature Electronics, Published online: 04 May 2023; doi:10.1038/s41928-023-00959-3

Ferroelectric zirconium-doped hafnia (Hf0.5Zr0.5O2) can be used to create negative differential capacitance behaviour in capacitors and transistor gate stacks, providing reliable enhancements in switching performance.

MoS₂ Transistors

As reported in article number 2210735, Yonghuang Wu, Zeqin Xin, Kai Liu, and co-workers build harsh-environment-resistant MoS₂ transistors by engineering electrode–channel interfaces. The transistors are resistant to high temperature of 350 °C, 100% relative humidity, and oxidizing environments, paving the way toward nanoscale devices working in harsh environments, for example in aerospace applications.

With the assistance of a small STT current across the MTJ stack during SOT, field-free deterministic SOT switching is realized, and the critical switching current density of SOT decreases with increasing the STT current density. TI-pMTJ devices with perpendicular magnetic anisotropy have much higher thermal stability and much lower switching current density, to realize SOT-MRAM applications.

Abstract

Giant spin–orbit torque (SOT) from topological insulators (TIs) has great potential for low-power SOT-driven magnetic random-access memory (SOT-MRAM). In this work, a functional 3-terminal SOT-MRAM device is demonstrated by integrating the TI [(BiSb)₂Te₃] with perpendicular magnetic tunnel junctions (pMTJs), where the tunneling magnetoresistance is employed for the effective reading method. An ultralow switching current density of 1.5 × 10⁵ A cm⁻² is achieved in the TI-pMTJ device at room temperature, which is 1–2 orders of magnitude lower than that in conventional heavy–metals-based systems, due to the high SOT efficiency θ _SH = 1.16 of (BiSb)₂Te₃. Furthermore, all-electrical field-free writing is realized by the synergistic effect of a small spin-transfer torque current during the SOT. The thermal stability factor (Δ = 66) shows the high retention time (>10 years) of the TI-pMTJ device. This work sheds light to the future low-power, high-density, and high-endurance/retention magnetic memory technology based on quantum materials.

Nature Materials, Published online: 03 May 2023; doi:10.1038/s41563-023-01536-x

Antiferromagnetism has a vanishing total magnetization and thus is extremely challenging to manipulate. Now, circularly polarized light is shown to efficiently detect, induce and switch a unique class of antiferromagnets.

Nature, Published online: 03 May 2023; doi:10.1038/s41586-023-05889-w

A new transfer method for microLEDs fabrication based on fluidic self-assembly technology combining magnetic and dielectrophoresis forces is described, achieving a very high simultaneous RGB LED transfer yield and over large areas.

Nature, Published online: 03 May 2023; doi:10.1038/s41586-023-05853-8

All-optical, mode-selective manipulation of the crystal lattice can be used to enhance and stabilize ferromagnetism in YTiO3 well above its equilibrium ordering temperature and for many nanoseconds, enabling dynamic engineering of practically useful non-equilibrium functionalities in fluctuating electronic systems.

Nature Electronics, Published online: 03 May 2023; doi:10.1038/s41928-023-00958-4

Despite advances in speech processing systems, such as those used in voice-controlled devices, human hearing still outperforms technical systems in noisy and variable environments. To close this gap, a bioinspired acoustic sensor with integrated signal processing was developed — the dynamic microelectromechanical system (MEMS)-based cochlea.

Nature Communications, Published online: 29 April 2023; doi:10.1038/s41467-023-37917-8

Applications of van der Waals magnetic systems are typically hampered by the low Curie temperature of van der Waals magnets. Here, Wang et al use molecular beam epitaxy to grow large films of Fe4GeTe2 with Curie temperatures over 500 K, and the film’s magnetic anisotropy can be tuned arbitrarily by controlling stoichiometry.

In this letter, we propose a mechanism to control the magnetic properties of topological quantum material (TQM) by using magnetoelectric coupling: this mechanism uses a heterostructure of TQM with two-dimensional (2D) ferroelectric material, which can dynamically control the magnetic order by changing the polarization of the ferroelectric material and induce possible topological phase transitions. This concept is demonstrated using the example of the bilayer MnBi2Te4 on ferroelectric In2Se3 or In2Te3, where the polarization direction of the 2D ferroelectrics determines the interfacial band alignment and consequently the direction of the charge transfer. This charge transfer, in turn, enhances the stability of the ferromagnetic state of MnBi2Te4 and leads to a possible topological phase transition between the quantum anomalous Hall (QAH) effect and the zero plateau QAH. Our work provides a route to dynamically alter the magnetic ordering of TQMs and could lead to the discovery of new multifunctional topological heterostructures.

Nature, Published online: 03 May 2023; doi:10.1038/d41586-023-01460-9

A device that transforms infrared light into a visible image could be used for anti-surveillance purposes.

Columnar grain boundaries in donor-doped perovskite oxide thin films can scatter and filter electrons, serve as VO··$V_{\rm{O}}^{\cdot\cdot}$ diffusion paths, leading to increased carrier concentration, increased effective mass, and decreased carrier mobility. By orientation modulation, the growth mode and grain boundary morphologies can be tuned to obtain competitive weighted mobility of 71.9 cm² V⁻¹ s⁻¹ (RT) and PF_max of 791 µW m⁻¹ K⁻² (573 K) among n-type oxides.

Abstract

Thermoelectric oxide thin films are promising in chip cooling. The issues on the orientation of thin films are essential as they are related to the structures, morphologies, and thermoelectric properties. In this regard, the orientation modulation is conducted on La-doped SrTiO₃ thin films on (LaAlO₃)_0.3(Sr₂TaAlO₆)_0.7 (LSAT) single crystal substrates. Layer-by-layer growth mode is found in (001)- and (110)- oriented thin films, resulting in few grain boundaries (GBs). In (111)-oriented films, island growth mode leads to columnar grain boundaries that build up potential barriers for electrons to be strongly scattered and filtered, suppressing electron mobility and increasing effective mass. In addition, the GBs serve as oxygen vacancy diffusion paths when annealing, causing increased carrier concentration and lattice contraction. The weighted mobility of 71.9 cm² V⁻¹ s⁻¹ and electrical conductivity of ≈600 S cm⁻¹ are realized in the (001)-oriented film at room temperature. Ultimately, outstanding power factor values of ≈569 µW m⁻¹ K⁻² (room temperature) and ≈791 µW m⁻¹ K⁻² (573 K) are successfully achieved, outperforming those in polycrystalline ceramics and (111)-oriented films. This study systematically investigates the influence of grain boundaries and orientations on SrTiO₃-based thermoelectric films, which lays a solid foundation for improving thermoelectric performance in other oxide thin films.

Advanced Functional Materials, Volume 33, Issue 18, May 2, 2023.