Shared posts
[ASAP] Is Graphene Oxide a Chemoattractant?
[ASAP] Revealing the Local Electronic Structure of a Single-Layer Covalent Organic Framework through Electronic Decoupling
[ASAP] Stochastic Stress Jumps Due to Soliton Dynamics in Two-Dimensional van der Waals Interfaces
[ASAP] Alkali Cation Doping for Improving the Structural Stability of 2D Perovskite in 3D/2D PSCs
[ASAP] Borophene Concentric Superlattices via Self-Assembly of Twin Boundaries
[ASAP] Direct Observation of the Linear Dichroism Transition in Two-Dimensional Palladium Diselenide
[ASAP] Treating Acute Kidney Injury with Antioxidative Black Phosphorus Nanosheets
[ASAP] van der Waals Integrated Devices Based on Nanomembranes of 3D Materials
[ASAP] From 2D STXM to 3D Imaging: Soft X-ray Laminography of Thin Specimens
[ASAP] Negatively Charged Excitons in CdSe Nanoplatelets
[ASAP] Double Moiré with a Twist: Supermoiré in Encapsulated Graphene
[ASAP] Frictional Drag Effect between Massless and Massive Fermions in Single-Layer/Bilayer Graphene Heterostructures
[ASAP] Localized Heating and Switching in MoTe2-Based Resistive Memory Devices
[ASAP] Uniaxial Strain-Controlled Ground States in Manganite Films
[ASAP] In Situ Observation of Vapor-Assisted 2D–3D Heterostructure Formation for Stable and Efficient Perovskite Solar Cells
[ASAP] Nanoscale Mapping of the Double Layer Potential at the Graphene–Electrolyte Interface
[ASAP] Temperature-Driven Transformation of CsPbBr3 Nanoplatelets into Mosaic Nanotiles in Solution through Self-Assembly
[ASAP] Nonlinear Optics at Excited States of Exciton Polaritons in Two-Dimensional Atomic Crystals
[ASAP] Two-Dimensionally Stretchable Organic Light-Emitting Diode with Elastic Pillar Arrays for Stress Relief
[ASAP] Multiband Hypersound Filtering in Two-Dimensional Colloidal Crystals: Adhesion, Resonances, and Periodicity
[ASAP] Ultrasensitive Plasmon-Free Surface-Enhanced Raman Spectroscopy with Femtomolar Detection Limit from 2D van der Waals Heterostructure
[ASAP] Magnetic Anisotropy of a Quasi Two-Dimensional Canted Antiferromagnet
[ASAP] Scalable Fabrication of Quasi-One-Dimensional Gold Nanoribbons for Plasmonic Sensing
Nearly room temperature ferromagnetism in a magnetic metal-rich van der Waals metal
In spintronics, two-dimensional van der Waals crystals constitute a most promising material class for long-distance spin transport or effective spin manipulation at room temperature. To realize all-vdW-material–based spintronic devices, however, vdW materials with itinerant ferromagnetism at room temperature are needed for spin current generation and thereby serve as an effective spin source. We report theoretical design and experimental realization of a iron-based vdW material, Fe4GeTe2, showing a nearly room temperature ferromagnetic order, together with a large magnetization and high conductivity. These properties are well retained even in cleaved crystals down to seven layers, with notable improvement in perpendicular magnetic anisotropy. Our findings highlight Fe4GeTe2 and its nanometer-thick crystals as a promising candidate for spin source operation at nearly room temperature and hold promise to further increase Tc in vdW ferromagnets by theory-guided material discovery.
Ultrafast x-ray diffraction study of melt-front dynamics in polycrystalline thin films
Melting is a fundamental process of matter that is still not fully understood at the microscopic level. Here, we use time-resolved x-ray diffraction to examine the ultrafast melting of polycrystalline gold thin films using an optical laser pump followed by a delayed hard x-ray probe pulse. We observe the formation of an intermediate new diffraction peak, which we attribute to material trapped between the solid and melted states, that forms 50 ps after laser excitation and persists beyond 500 ps. The peak width grows rapidly for 50 ps and then narrows distinctly at longer time scales. We attribute this to a melting band originating from the grain boundaries and propagating into the grains. Our observation of this intermediate state has implications for the use of ultrafast lasers for ablation during pulsed laser deposition.
Bright magnetic dipole radiation from two-dimensional lead-halide perovskites
Light-matter interactions in semiconductors are uniformly treated within the electric dipole approximation; multipolar interactions are considered "forbidden." We experimentally demonstrate that this approximation inadequately describes light emission in two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs), solution processable semiconductors with promising optoelectronic properties. By exploiting the highly oriented crystal structure, we use energy-momentum spectroscopies to demonstrate that an exciton-like sideband in 2D HOIPs exhibits a multipolar radiation pattern with highly directed emission. Electromagnetic and quantum-mechanical analyses indicate that this emission originates from an out-of-plane magnetic dipole transition arising from the 2D character of electronic states. Symmetry arguments and temperature-dependent measurements suggest a dynamic symmetry-breaking mechanism that is active over a broad temperature range. These results challenge the paradigm of electric dipole–dominated light-matter interactions in optoelectronic materials, provide new perspectives on the origins of unexpected sideband emission in HOIPs, and tease the possibility of metamaterial-like scattering phenomena at the quantum-mechanical level.
High mobility in a van der Waals layered antiferromagnetic metal
Van der Waals (vdW) materials with magnetic order have been heavily pursued for fundamental physics as well as for device design. Despite the rapid advances, so far, they are mainly insulating or semiconducting, and none of them has a high electronic mobility—a property that is rare in layered vdW materials in general. The realization of a high-mobility vdW material that also exhibits magnetic order would open the possibility for novel magnetic twistronic or spintronic devices. Here, we report very high carrier mobility in the layered vdW antiferromagnet GdTe3. The electron mobility is beyond 60,000 cm2 V–1 s–1, which is the highest among all known layered magnetic materials, to the best of our knowledge. Among all known vdW materials, the mobility of bulk GdTe3 is comparable to that of black phosphorus. By mechanical exfoliation, we further demonstrate that GdTe3 can be exfoliated to ultrathin flakes of three monolayers.
Ultrasensitive and ultrathin phototransistors and photonic synapses using perovskite quantum dots grown from graphene lattice
Organic-inorganic halide perovskite quantum dots (PQDs) constitute an attractive class of materials for many optoelectronic applications. However, their charge transport properties are inferior to materials like graphene. On the other hand, the charge generation efficiency of graphene is too low to be used in many optoelectronic applications. Here, we demonstrate the development of ultrathin phototransistors and photonic synapses using a graphene-PQD (G-PQD) superstructure prepared by growing PQDs directly from a graphene lattice. We show that the G-PQDs superstructure synchronizes efficient charge generation and transport on a single platform. G-PQD phototransistors exhibit excellent responsivity of 1.4 x 108 AW–1 and specific detectivity of 4.72 x 1015 Jones at 430 nm. Moreover, the light-assisted memory effect of these superstructures enables photonic synaptic behavior, where neuromorphic computing is demonstrated by facial recognition with the assistance of machine learning. We anticipate that the G-PQD superstructures will bolster new directions in the development of highly efficient optoelectronic devices.
Widely tunable mid-infrared light emission in thin-film black phosphorus
Thin-film black phosphorus (BP) is an attractive material for mid-infrared optoelectronic applications because of its layered nature and a moderate bandgap of around 300 meV. Previous photoconduction demonstrations show that a vertical electric field can effectively reduce the bandgap of thin-film BP, expanding the device operational wavelength range in mid-infrared. Here, we report the widely tunable mid-infrared light emission from a hexagonal boron nitride (hBN)/BP/hBN heterostructure device. With a moderate displacement field up to 0.48 V/nm, the photoluminescence (PL) peak from a ~20-layer BP flake is continuously tuned from 3.7 to 7.7 μm, spanning 4 μm in mid-infrared. The PL emission remains perfectly linear-polarized along the armchair direction regardless of the bias field. Moreover, together with theoretical analysis, we show that the radiative decay probably dominates over other nonradiative decay channels in the PL experiments. Our results reveal the great potential of thin-film BP in future widely tunable, mid-infrared light-emitting and lasing applications.
Uniform hierarchical MFI nanosheets prepared via anisotropic etching for solution-based sub-100-nm-thick oriented MFI layer fabrication
Zeolite nanosheets have shown unprecedented opportunities for a wide range of applications, yet developing facile methods for fabrication of uniform zeolite nanosheets remains a great challenge. Here, a facile approach involving anisotropic etching with an aqueous solution of tetrapropylammonium hydroxide (TPAOH) was developed for preparing uniform high–aspect ratio hierarchical MFI nanosheets. In addition, the mechanism associated with the formation of MFI nanosheets was proposed. In the next step, a dynamic air-liquid interface–assisted self-assembly method and single-mode microwave heating were used for b-oriented MFI nanosheets monolayer deposition and controlled in-plane solution-based epitaxial growth, respectively, ensuring the formation of well-intergrown b-oriented MFI layers with sub–100-nm thickness. Moreover, our study indicated that b-oriented ultrathin MFI layers could be fabricated on diverse substrates demonstrating excellent anticorrosion capacity, ionic sieving properties, and n-/i-butane isomer separation performance.