Jiuxiang Dai

Author(s): Zhihao Zang, Yaozheng Zhu, Ming Xi, Shangjie Tian, Tingting Wang, Pingfan Gu, Yuxuan Peng, Shiqi Yang, Xiaolong Xu, Yanping Li, Bo Han, Liwei Liu, Yeliang Wang, Peng Gao, Jinbo Yang, Hechang Lei, Yuan Huang, and Yu Ye

MnBi2Te4, an intrinsic magnetic topological insulator, has shown layer-number-correlated magnetic and topological phases. More interestingly, in the isostructural material MnSb2Te4, the antiferromagnetic (AFM) and ferromagnetic (FM) states have been both observed in the bulk counterparts, which are ...

[Phys. Rev. Lett. 128, 017201] Published Mon Jan 03, 2022

A high-entropy carbonitride MAX phase is synthesized on the basis of metallurgical treatment of a medium-entropy MAX phase with other MAX phases. After the selective etching of Al species, the derivative high-entropy carbonitride MXene is achieved, in which there are strong mechanical strains by implanting five types of transition metals, showing high electrocatalytic activities for polysulfides in lithium–sulfur batteries.

Abstract

Although high-entropy layered transition metal carbonitride MAX phases and their derivative MXenes have been proposed to exhibit unique physicochemical features for widespread applications, it is still challenging to synthesize them owing to the easy formation of separated phases during the traditional synthetic process. Here, a new high-entropy carbonitride MAX phase (HE CN-MAX, (Ti_1/3V_1/6Zr_1/6Nb_1/6Ta_1/6)₂AlC_xN_1–x) is synthesized on the basis of metallurgically treating medium-entropy MAX (ME-MAX) (Zr_1/3Nb_1/3Ta_1/3)₂AlC and other MAX phases (Ti₄AlN₃ and V₂AlC). During the metallurgical process, the unique usage of a medium-entropy MAX phase effectively solves the phase separation issue for the formation of a high-entropy MAX phase owing to their low entropy difference. After selective extraction of an A species, a high-entropy carbonitride MXene (HE CN-MXene) with high mechanical strains and five types of metal-nitrogen bonds is achieved, which shows good adsorption and catalytic activities for lithium polysulfides. As a result, a lithium–sulfur battery with HE CN-MXene delivers a high-rate capability (702 mAh g⁻¹ at 4 C) and good cycling stability.

2D materials show great potential in building infrared (IR) photodetectors thanks to their fascinating optoeletronic properties. In this review, the state-of-the-art progress of IR photodetectors is comprehensively summarized based on 2D materials and nanophotonic structures.

Abstract

2D materials, such as graphene, transition metal dichalcogenides, black phosphorus, and tellurium, have been demonstrated to be promising building blocks for the fabrication of next-generation high-performance infrared (IR) photodetectors with diverse device architectures and impressive device performance. Integrating IR photodetectors with nanophotonic structures, such as surface plasmon structures, optical waveguides, and optical cavities, has proven to be a promising strategy to maximize the light absorption of 2D absorbers, thus enhancing the detector performance. In this review, the state-of-the-art progress of IR photodetectors is comprehensively summarized based on 2D materials and nanophotonic structures. First, the advantages of using 2D materials for IR photodetectors are discussed. Following that, 2D material-based IR detectors are classified based on their composition, and their detection mechanisms, key figures-of-merit, and the principle of absorption enhancement are discussed using nanophotonic approaches. Then, recent advances in 2D material-based IR photodetectors are reviewed, categorized by device architecture, i.e., photoconductors, van der Waals heterojunctions, and hybrid systems consisting of 2D materials and nanophotonic structures. The review is concluded by providing perspectives on the challenges and future directions of this field.

This work reports a broadband photodetector utilizing GaTe after breaking through its bandgap limitation by self-driven O₂ intercalation in air and further reveals its anisotropic nature of the photoconductivity. This provides design strategies of 2D materials-based high performance broadband photodetectors for the exploration of the polarized state information.

Abstract

Low symmetric two dimensional (2D) semiconductors are of great significance for their potential applications in polarization-sensitive photodetection and quantum information devices. However, their real applications are limited by their photo-detecting wavelength ranges, which are restricted by their fundamental optical bandgaps. Recently, intercalation has been demonstrated to be a powerful strategy to modulate the optical bandgaps of 2D semiconductors. Here, the authors report the self-driven oxygen (O₂) intercalation induced bandgap reduction from 1.75 to 1.19 eV in gallium telluride (GaTe) in air. This bandgap shrinkage provides the long-wavelength detection threshold above ≈1100 nm for O₂ intercalated GaTe (referred to as GaTeO₂), well beyond the cut-off wavelength at ≈708 nm for pristine GaTe. The GaTeO₂ photodetectors have a high photoresponsivity, and highly anisotropic photodetection behavior to even sub-waveband radiation. The dichroic ratio (I _max /I _min) of photocurrent is about 1.39 and 2.9 for 600 nm and 1100 nm, respectively. This findings demonstrates a broadband photodetector utilizing GaTe after breaking through its bandgap limitation by self-driven O₂ intercalation in air and further reveal its photoconductivity anisotropic nature. This provides design strategies of 2D materials-based high-performance broadband photodetectors for the exploration of polarized state information.

The combination of nanogenerator and biomedicine have been accelerating the development of self-powered biomedical devices, which show a bright future in biomedicine and healthcare such as smart sensing, and therapy.

The dream of human beings for long living has stimulated the rapid development of biomedical and healthcare equipment. However, conventional biomedical and healthcare devices have shortcomings such as short service life, large equipment size, and high potential safety hazards. Indeed, the power supply for conventional implantable device remains predominantly batteries. The emerging nanogenerators, which harvest micro/nanomechanical energy and thermal energy from human beings and convert into electrical energy, provide an ideal solution for self-powering of biomedical devices. The combination of nanogenerators and biomedicine has been accelerating the development of self-powered biomedical equipment. This article first introduces the operating principle of nanogenerators and then reviews the progress of nanogenerators in biomedical applications, including power supply, smart sensing, and effective treatment. Besides, the microbial disinfection and biodegradation performances of nanogenerators have been updated. Next, the protection devices have been discussed such as face mask with air filtering function together with real-time monitoring of human health from the respiration and heat emission. Besides, the nanogenerator devices have been categorized by the types of mechanical energy from human beings, such as the body movement, tissue and organ activities, energy from chemical reactions, and gravitational potential energy. Eventually, the challenges and future opportunities in the applications of nanogenerators are delivered in the conclusive remarks.

Monolayer molybdenum disulfide (MoS 2 ) is one of the most studied two-dimensional (2D) transition metal dichalcogenides that is being investigated for various optoelectronic properties, such as catalysis, sensors, photovoltaics, and batteries. One such property that makes this material attractive is the ease in which 2D MoS 2 can be converted between the semiconducting (2H) and metallic/semi-metallic (1T/1T′) phases or heavily n-type doped 2H phase with ion intercalation, strain, or excess negative charge. Using n -butyl lithium (BuLi) immersion treatments, we achieve 2H MoS 2 monolayers that are heavily n-type doped with shorter immersion times (10–120 mins) or conversion to the 1T/1T′ phase with longer immersion times (6–24 h); however, these doped/converted monolayers are not stable and promptly revert back to the initial 2H phase upon exposure to air. To overcome this issue and maintain the modification of the monolayer MoS 2 upo...

Despite the various techniques developed for the transfer of large area graphene grown by chemical vapor deposition (CVD), the conventional polymethylmethacrylate (PMMA) transferring technique has been widely applied in laboratories due to its convenience and economical cost. However, the complete removal of PMMA on graphene surface has become a troublesome, and the PMMA residue could degrade the properties of graphene significantly. We report here a facile water assisted technique to directly peel off the PMMA layer over centimeter-sized CVD graphene film for the first time. No organic solvents are involved in the whole transfer process. The transferred graphene film is clean and intact over large area because of the cooperative effect of the capillary force and the van der Waals force which facilitates the conformal contact between graphene film and the substrate. Various types of graphene samples (i.e. monolayer, multilayer, and incomplete domains) can be easily transferred t...

During the past decade, two-dimensional materials have attracted much attention in superconductivity due to their feasible physical properties and easy chemical modifications. Herein, we use a recently literature reported novel biphenylene sheet (BP sheet) for investigating superconductivity-related physical properties. The electronic states of BP sheet that appeared near the Fermi level are composed of p z orbital of carbon due to sp 2 hybridization. Also, an anisotropic Dirac cone is formed just above the Fermi level by crossing two bands comprised of different carbon atoms. One of the two bands is quasi-flat thus leading to a peak of electronic density of states above the Fermi level. In addition, the rotational-vibration phonon mode of the six-membered carbon ring is strongly coupled with electrons. The electron-phonon coupling induces the superconductivity of 6.2 K in BP sheet. Furthermore, both small uniaxial strains and electronic doping can t...

Light: Science & Applications, Published online: 02 January 2022; doi:10.1038/s41377-021-00694-4

Van der Waals two-color infrared photodetector

This review introduces current progress of 2D materials (2DM) application in all-solid-state lithium batteries (ASSLB) to deal with the limitation of ASSLBs. 2DMs are applied in the different composition of the ASSLBs to enhance its performance. By summarizing the properties, synthesis, application, and characterization, this review points out the future development direction of 2DMs application in ASSLBs.

Abstract

Although one of the most mature battery technologies, lithium-ion batteries still have many aspects that have not reached the desired requirements, such as energy density, current density, safety, environmental compatibility, and price. To solve these problems, all-solid-state lithium batteries (ASSLB) based on lithium metal anodes with high energy density and safety have been proposed and become a research hotpot in recent years. Due to the advanced electrochemical properties of 2D materials (2DM), they have been applied to mitigate some of the current problems of ASSLBs, such as high interface impedance and low electrolyte ionic conductivity. In this work, the background and fabrication method of 2DMs are reviewed initially. The improvement strategies of 2DMs are categorized based on their application in the three main components of ASSLBs: The anode, cathode, and electrolyte. Finally, to elucidate the mechanisms of 2DMs in ASSLBs, the role of in situ characterization, synchrotron X-ray techniques, and other advanced characterization are discussed.

If a truly multifunctional material with a large spin-orbit coupling is looked for, it would be hard to beat KTaO₃ (KTO). The 2D electron gas housed by KTO-based thin films and heterostructures exhibits spin-polarization, ferroelectricity, superconductivity, persistent photocurrent, etc., and provides a platform to realize exotic relativistic quantum particles. Read this state-of-the-art review for all the fascinating details.

Abstract

Long after the heady days of high-temperature superconductivity, the oxides came back into the limelight in 2004 with the discovery of the 2D electron gas (2DEG) in SrTiO₃ (STO) and several heterostructures based on it. Not only do these materials exhibit interesting physics, but they have also opened up new vistas in oxide electronics and spintronics. However, much of the attention has recently shifted to KTaO₃ (KTO), a material with all the “good” properties of STO (simple cubic structure, high mobility, etc.) but with the additional advantage of a much larger spin-orbit coupling. In this state-of-the-art review of the fascinating world of KTO, it is attempted to cover the remarkable progress made, particularly in the last five years. Certain unsolved issues are also indicated, while suggesting future research directions as well as potential applications. The range of physical phenomena associated with the 2DEG trapped at the interfaces of KTO-based heterostructures include spin polarization, superconductivity, quantum oscillations in the magnetoresistance, spin-polarized electron transport, persistent photocurrent, Rashba effect, topological Hall effect, and inverse Edelstein Effect. It is aimed to discuss, on a single platform, the various fabrication techniques, the exciting physical properties and future application possibilities of this family of materials.

Author(s): R. Krause, S. Aeschlimann, M. Chávez-Cervantes, R. Perea-Causin, S. Brem, E. Malic, S. Forti, F. Fabbri, C. Coletti, and I. Gierz

Van der Waals heterostructures show many intriguing phenomena including ultrafast charge separation following strong excitonic absorption in the visible spectral range. However, despite the enormous potential for future applications in the field of optoelectronics, the underlying microscopic mechani...

[Phys. Rev. Lett. 127, 276401] Published Mon Dec 27, 2021