Jiuxiang Dai

Nature Nanotechnology, Published online: 25 June 2024; doi:10.1038/s41565-024-01696-0

Highlights

• Ferroelectricity and domain dynamics of emerging ferroelectric AlScN films were discussed.

• The performance optimization of ferroelectric AlScN films grown by different deposition techniques was comprehensively analyzed.

• The challenges and perspectives regarding the commercial avenue of AlScN-based memories and in-memory computing applications were summarized.

The intercalation of large organic molecules decouples the interlayer interaction of VOCl and induces the intralayer ferromagnetic (FM) coupling. Meanwhile, the intercalation also guides the charge injection, promotes the hybridization of 3d orbital electrons, and further strengthens the FM interaction, ultimately achieving the transition from pristine antiferromagnetism to room-temperature ferromagnetism with out-of-plane anisotropy.

Abstract

2D van der Waals (vdW) magnets are gaining attention in fundamental physics and advanced spintronics, due to their unique dimension-dependent magnetism and potential for ultra-compact integration. However, achieving intrinsic ferromagnetism with high Curie temperature (T _C) remains a technical challenge, including preparation and stability issues. Herein, an applicable electrochemical intercalation strategy to decouple interlayer interaction and guide charge doping in antiferromagnet VOCl, thereby inducing robust room-temperature ferromagnetism, is developed. The expanded vdW gap isolates the neighboring layers and shrinks the distance between the V-V bond, favoring the generation of ferromagnetic (FM) coupling with perpendicular magnetic anisotropy. Element-specific X-ray magnetic circular dichroism (XMCD) directly proves the source of the ferromagnetism. Detailed experimental results and density functional theory (DFT) calculations indicate that the charge doping enhances the FM interaction by promoting the orbital hybridization between t _{2 g} and e_g . This work sheds new light on a promising way to achieve room-temperature ferromagnetism in antiferromagnets, thus addressing the critical materials demand for designing spintronic devices.

Cs₃CeCl₆ (CCC) nanocrystals (NCs) possess fascinating optical properties due to their f–d coupling of Ce³⁺ ions. The incorporation of Gd³⁺ in CCC NCs can be a facile method to enhance photoluminescence quantum yield (PLQY) up to almost unity (96%) as well as the phase stability. This Cs₃Ce_{1- x} Gd _x Cl₆ alloyed NCs exhibits efficient device performance as a UV-light absorbing layer for photodetector with detectivity (7.938 × 10¹¹ Jones) and responsivity (0.195 A W⁻¹) at -0.1 V bias at 310 nm.

Abstract

Recently, lanthanide-based 0D metal halides have attracted considerable attention for their applications in X-ray imaging, light-emitting diodes (LEDs), sensors, and photodetectors. Herein, lead-free 0D gadolinium-alloyed cesium cerium chloride (Gd³⁺-alloyed Cs₃CeCl₆) nanocrystals (NCs) are introduced as promising materials for optoelectronic application owing to their unique optical properties. The incorporation of Gd³⁺ in Cs₃CeCl₆ (CCC) NCs is proposed to increase the photoluminescence quantum yield (PLQY) from 57% to 96%, along with significantly enhanced phase and chemical stability. The structural analysis is performed by density functional theory (DFT) to confirm the effect of Gd³⁺ in Cs₃Ce_{1- x} Gd _x Cl₆ (CCGC) alloy system. Moreover, the CCGC NCs are applied as the active layer in UVPDs with different Gd³⁺ concentration. The excellent device performance is shown at 20% of Gd³⁺ in CCGC NCs with high detectivity (7.938 × 10¹¹ Jones) and responsivity (0.195 A W⁻¹) at -0.1 V at 310 nm. This study paves the way for the development of lanthanide-based metal halide NCs for next-generation UVPDs and other optoelectronic applications.

An inductive coupled plasma treatment method is developed to introduce defects in h-BN, which further influence the interfacial charge transfer behavior between graphene/h-BN/WS₂ heterostructures. Besides, the photo-response performance of the heterostructure-based photodetector, including photocurrent amplitude, light on/off ratio, and self-driving performance, is highly improved by means of defect engineering.

Abstract

At the interface of 2D heterostructures, the presence of defects and their manipulation play a crucial role in the interfacial charge transfer behavior, further influencing the device functionality and performance. In this study, the impact of deliberately introduced photo-active defects in the h-BN layer on the interfacial charge transfer and photoresponse performance of a metal-insulator-semiconductor type heterostructure device is explored. The formation and concentration of defects are qualitatively controlled using an inductive coupled plasma treatment method, as evidenced by enhanced h-BN defect emission and more efficient optically induced doping of graphene at the graphene/h-BN interface. Besides, the use of the h-BN layer between graphene and WS₂ not only suppresses charge carriers in the dark state, but also promotes the separation of photo-generated electron-hole pairs and interfacial charge transfer due to the existence of defect levels, leading to orders of magnitude improvement in the light on/off ratio and self-driving performance of the heterostructure photodetector. This strategy of controlling defect states in the insulating layer provides a new approach to optimize the charge transfer processes at the 2D interfaces, so as to expand its potential applications in the fields of electronic and optoelectronic devices.

Publication date: December 2024

Source: Progress in Materials Science, Volume 146

Author(s): Prashant Kumar, Gurwinder Singh, Rohan Bahadur, Zhixuan Li, Xiangwei Zhang, C.I. Sathish, Mercy R. Benzigar, Thi Kim Anh Tran, Nisha T. Padmanabhan, Sithara Radhakrishnan, Jith C Janardhanan, Christy Ann Biji, Ann Jini Mathews, Honey John, Ehsan Tavakkoli, Ramaswamy Murugavel, Soumyabrata Roy, Pulickel M. Ajayan, Ajayan Vinu

This study reports the enhanced lattice oxygen participation in P-incorporated double perovskite oxides LaNi_0.58Fe_0.38P_0.07O_3-σ (PLNFO) for boosting water oxidation. The substitution of P upshifts the O p band center and enhances the hybridization, making the electronic states near the Fermi level with substantial O 2p character, which aggravate the lattice oxygen participation mechanism (LOM) pathway, and thus accelerate the oxygen-evoluting kinetics.

Abstract

Activating the lattice oxygen in the catalysts to participate in the oxygen evolution reaction (OER), which can break the scaling relation–induced overpotential limitation (> 0.37 V) of the adsorbate evolution mechanism, has emerged as a new and highly effective guide to accelerate the OER. However, how to increase the lattice oxygen participation of catalysts during OER remains a major challenge. Herein, P-incorporation induced enhancement of lattice oxygen participation in double perovskite LaNi_0.58Fe_0.38P_0.07O_3-σ (PLNFO) is studied. P-incorporation is found to be crucial for enhancing the OER activity. The current density reaches 1.35 mA cm_ECSA ⁻² at 1.63 V (vs RHE), achieving a sixfold increase in intrinsic activity. Experimental evidences confirm the dominant lattice oxygen participation mechanism (LOM) for OER pathway on PLNFO. Further electronic structures reveal that P-incorporation shifts the O p-band center by 0.7 eV toward the Fermi level, making the states near the Fermi level more O p character, thus facilitating LOM and fast OER kinetics. This work offers a possible method to develop high-performance double perovskite OER catalysts for electrochemical water splitting.

The proposed strategy that combines magnetic and optical fields to achieve independent position control and task execution of multiple microrobotic collectives in 3D space. The magnetic field excites the self-assembly of colloids and maintains the self-assembled microrobotic collectives without disassembly, while the optical field drives selected microrobotic collectives to perform different tasks.

Abstract

Inspired by natural swarms, various methods are developed to create artificial magnetic microrobotic collectives. However, these magnetic collectives typically receive identical control inputs from a common external magnetic field, limiting their ability to operate independently. And they often rely on interfaces or boundaries for controlled movement, posing challenges for independent, three-dimensional(3D) navigation of multiple magnetic collectives. To address this challenge, self-assembled microrobotic collectives are proposed that can be selectively actuated in a combination of external magnetic and optical fields. By harnessing both actuation methods, the constraints of single actuation approaches are overcome. The magnetic field excites the self-assembly of colloids and maintains the self-assembled microrobotic collectives without disassembly, while the optical field drives selected microrobotic collectives to perform different tasks. The proposed magnetic-photo microrobotic collectives can achieve independent position and path control in the two-dimensional (2D) plane and 3D space. With this selective control strategy, the microrobotic collectives can cooperate in convection and mixing the dye in a confined space. The results present a systematic approach for realizing selective control of multiple microrobotic collectives, which can address multitasking requirements in complex environments.

This review begins by introducing the mechanisms underlying the formation of amorphous structures. Subsequently, it provides an overview of characterization methods employed to identify amorphous species. The review also covers strategies for regulating the amorphization process by modifying the intrinsic properties of catalysts and adjusting external electrochemical conditions. Furthermore, the review delves into the involvement of in situ generated amorphous species in electrochemical processes. However, there are challenges and opportunities in comprehending the in situ amorphization process and regulating the formation of highly active amorphous species.

Abstract

Electrocatalysis represents an efficient and eco-friendly approach to energy conversion, enabling the sustainable synthesis of valuable chemicals and fuels. The deliberate engineering of electrocatalysts is crucial to improving the efficacy and scalability of electrocatalysis. Notably, the occurrence of in situ amorphization within electrocatalysts has been observed during various electrochemical processes, influencing the energy conversion efficiency and catalytic mechanism understanding. Of note, the dynamic transformation of catalysts into amorphous structures is complex, often leading to various amorphous configurations. Therefore, revealing this amorphization process and understanding the function of amorphous species are pivotal for elucidating the structure-activity relationship of electrocatalysts, which will direct the creation of highly efficient catalysts. This review examines the mechanisms behind amorphous structure formation, summarizes characterization methods for detecting amorphous species, and discusses strategies for controlling (pre)catalyst properties and electrochemical conditions that influence amorphization. It also emphasizes the importance of spontaneously formed amorphous species in electrochemical oxidation and reduction reactions. Finally, it addresses challenges in the in situ amorphization of electrocatalysts. aiming to guide the synthesis of electrocatalysts for efficient, selective, and stable electrochemical reactions, and to inspire future advancements in the field.

Flexible and transparent fully 2D materials based memristors exhibit reliable threshold resistive switching behavior with a high degree of stochasticity. A true random number generator circuit for advanced data encryption can be developed using the Graphene/hexagonal boron nitride/Graphene devices with high cycle-to-cycle variability of switching voltages and state currents as entropy source.

Abstract

Data encryption is an essential building block in modern electronic systems to prevent spying and hacking. Every day more and more objects produce electronic data, and this needs to be encrypted before being transmitted. Hence, designing devices, circuits, and systems for data encryption that can be integrated in all kinds of objects and that consume low amounts of energy is highly necessary. Here, this work reports the fabrication of flexible and transparent electronic circuits consisting of devices that exhibit threshold-type resistive switching with a high degree of stochasticity. The cycle-to-cycle variability of switching voltages and state currents is significant but confined within a well-defined range, which is consistent across multiple devices. This allows to design an efficient protocol for true random number generation. The circuits are fabricated with only synthetic 2D materials, can be fabricated in a scalable manner, and can be integrated in any object.

A new type of 2D metal halide perovskites is synthesized with a unique connectivity pattern. The unique class of perovskites showcases facile and reversible switching between glassy and crystalline states, accompanied by low crystallization activation energy. This characteristic paves the way for novel applications, including nonvolatile memory, optical communication, and neuromorphic computing.

Abstract

Crystalline metal halide perovskites (MHPs) have ushered in remarkable advancements across diverse fields, including materials, electronics, and photonics. While the advantages of crystallinity are well-established, the ability to transition to a glassy state with unique properties presents unprecedented opportunities to expand the structure-property relationship and broaden the application scope for 2D MHPs. Up until now, the exploration of amorphous analogs for MHPs is confined to high-pressure conditions, limiting in-depth studies and practical applications. In this context, a new type of 2D MHPs is synthesized by incorporating halogen substituted organic cations, resulting in a remarkable combination of low melting temperature and inhibited crystallization. This new type of 2D MHPs can be effectively melt-quenched into a glassy state except for (DMIEA)₃Pb₂I₇ (DMIEA = N, N-dimethyl iodoethylammonium) counterpart. Analysis of the crystallization activation energy for (DMIPA)₄Pb₃I₁₀ (DMIPA = N, N-dimethyl iodopropylammonium) reveals a low crystallization activation energy of 60.7 ± 4.0 kJ mol⁻¹, which indicates a fast glass-crystal transition. The type of atypical 2D MHP showcases facile and reversible switching between glassy and crystalline states and opens up novel possibilities for applications, such as nonvolatile memory, optical communication, and neuromorphic computing.

Nature, Published online: 26 June 2024; doi:10.1038/s41586-024-07457-2

Nature, Published online: 26 June 2024; doi:10.1038/s41586-024-07625-4

Nature, Published online: 26 June 2024; doi:10.1038/d41586-024-02111-3

Nature, Published online: 26 June 2024; doi:10.1038/s41586-024-07604-9

Nature Materials, Published online: 27 June 2024; doi:10.1038/s41563-024-01933-w

Nature, Published online: 27 June 2024; doi:10.1038/d41586-024-02098-x

Nature Electronics, Published online: 27 June 2024; doi:10.1038/s41928-024-01206-z

Nature Electronics, Published online: 27 June 2024; doi:10.1038/s41928-024-01187-z

Nature Electronics, Published online: 27 June 2024; doi:10.1038/s41928-024-01190-4