Shared posts
[ASAP] Synthetic Semimetals with van der Waals Interfaces
[ASAP] Electronic Polarizability as the Fundamental Variable in the Dielectric Properties of Two-Dimensional Materials
[ASAP] Exploitable Magnetic Anisotropy of the Two-Dimensional Magnet CrI3
[ASAP] Slippery and Wear-Resistant Surfaces Enabled by Interface Engineered Graphene
[ASAP] Observation of Magnetic Skyrmion Bubbles in a van der Waals Ferromagnet Fe3GeTe2
[ASAP] Perfect and Controllable Nesting in Minimally Twisted Bilayer Graphene
[ASAP] Optical Imaging and Spectroscopy of Atomically Precise Armchair Graphene Nanoribbons
Realization of 2D crystalline metal nitrides via selective atomic substitution
Two-dimensional (2D) transition metal nitrides (TMNs) are new members in the 2D materials family with a wide range of applications. Particularly, highly crystalline and large area thin films of TMNs are desirable for applications in electronic and optoelectronic devices; however, the synthesis of these TMNs has not yet been achieved. Here, we report the synthesis of few-nanometer thin Mo5N6 crystals with large area and high quality via in situ chemical conversion of layered MoS2 crystals. The versatility of this general approach is demonstrated by expanding the method to synthesize W5N6 and TiN. Our strategy offers a new direction for preparing 2D TMNs with desirable characteristics, opening a door for studying fundamental physics and facilitating the development of next-generation electronics.
[ASAP] Hexagonal Boron Nitride Synthesized at Atmospheric Pressure Using Metal Alloy Solvents: Evaluation as a Substrate for 2D Materials
[ASAP] Localized ZnO Growth on a Gold Nanoantenna by Plasmon-Assisted Hydrothermal Synthesis
[ASAP] Giant Valley-Zeeman Splitting from Spin-Singlet and Spin-Triplet Interlayer Excitons in WSe2/MoSe2 Heterostructure
[ASAP] Quantitative Nanoscale Absorption Mapping: A Novel Technique To Probe Optical Absorption of Two-Dimensional Materials
[ASAP] Ferroelectric Oxide Thin Film with an Out-of-Plane Electrical Conductivity
[ASAP] Precise Fabrication of De Novo Nanoparticle Lattices on Dynamic 2D Protein Crystalline Lattices
[ASAP] Interface-Charge Induced Giant Electrocaloric Effect in Lead Free Ferroelectric Thin-Film Bilayers
[ASAP] Few-Wall Carbon Nanotube Coils
[ASAP] Intrinsic 2D Ferromagnetism in V5Se8 Epitaxial Thin Films
[ASAP] Observation of the Kondo Effect in Multilayer Single-Crystalline VTe2 Nanoplates
[ASAP] Coexistence of Magnetic Orders in Two-Dimensional Magnet CrI3
[ASAP] Anomalous Angle-Dependent Magnetotransport Properties of Single InAs Nanowires
[ASAP] Shaping and Edge Engineering of Few-Layered Freestanding Graphene Sheets in a Transmission Electron Microscope
[ASAP] Magnetic Order-Induced Polarization Anomaly of Raman Scattering in 2D Magnet CrI3
[ASAP] Enhanced Piezoelectric Effect Derived from Grain Boundary in MoS2 Monolayers
[ASAP] Mode-Resolved Detection of Magnetization Dynamics Using X-ray Diffractive Ferromagnetic Resonance
[ASAP] Observation and Active Control of a Collective Polariton Mode and Polaritonic Band Gap in Few-Layer WS2 Strongly Coupled with Plasmonic Lattices
Transition metal dichalcogenides to the rescue
Nature Reviews Materials, Published online: 22 November 2019; doi:10.1038/s41578-019-0163-7
Transition metal dichalcogenides to the rescueNatural van der Waals heterostructural single crystals with both magnetic and topological properties
Heterostructures having both magnetism and topology are promising materials for the realization of exotic topological quantum states while challenging in synthesis and engineering. Here, we report natural magnetic van der Waals heterostructures of (MnBi2Te4)m(Bi2Te3)n that exhibit controllable magnetic properties while maintaining their topological surface states. The interlayer antiferromagnetic exchange coupling is gradually weakened as the separation of magnetic layers increases, and an anomalous Hall effect that is well coupled with magnetization and shows ferromagnetic hysteresis was observed below 5 K. The obtained homogeneous heterostructure with atomically sharp interface and intrinsic magnetic properties will be an ideal platform for studying the quantum anomalous Hall effect, axion insulator states, and the topological magnetoelectric effect.
Composite super-moire lattices in double-aligned graphene heterostructures
When two-dimensional (2D) atomic crystals are brought into close proximity to form a van der Waals heterostructure, neighbouring crystals may influence each other’s properties. Of particular interest is when the two crystals closely match and a moiré pattern forms, resulting in modified electronic and excitonic spectra, crystal reconstruction, and more. Thus, moiré patterns are a viable tool for controlling the properties of 2D materials. However, the difference in periodicity of the two crystals limits the reconstruction and, thus, is a barrier to the low-energy regime. Here, we present a route to spectrum reconstruction at all energies. By using graphene which is aligned to two hexagonal boron nitride layers, one can make electrons scatter in the differential moiré pattern which results in spectral changes at arbitrarily low energies. Further, we demonstrate that the strength of this potential relies crucially on the atomic reconstruction of graphene within the differential moiré super cell.
A new metal transfer process for van der Waals contacts to vertical Schottky-junction transition metal dichalcogenide photovoltaics
Two-dimensional transition metal dichalcogenides are promising candidates for ultrathin optoelectronic devices due to their high absorption coefficients and intrinsically passivated surfaces. To maintain these near-perfect surfaces, recent research has focused on fabricating contacts that limit Fermi-level pinning at the metal-semiconductor interface. Here, we develop a new, simple procedure for transferring metal contacts that does not require aligned lithography. Using this technique, we fabricate vertical Schottky-junction WS2 solar cells, with Ag and Au as asymmetric work function contacts. Under laser illumination, we observe rectifying behavior and open-circuit voltage above 500 mV in devices with transferred contacts, in contrast to resistive behavior and open-circuit voltage below 15 mV in devices with evaporated contacts. One-sun measurements and device simulation results indicate that this metal transfer process could enable high specific power vertical Schottky-junction transition metal dichalcogenide photovoltaics, and we anticipate that this technique will lead to advances for two-dimensional devices more broadly.
New classes of topological crystalline insulators having surface rotation anomaly
We discover new types of quantum anomalies in two-dimensional systems with time-reversal symmetry (T) and discrete rotation symmetry with order of n = 2, 4, and 6 (Cn). The new anomalous states have n flavors of massless Dirac fermions protected by T and Cn, whereas any two-dimensional lattices having the two symmetries must have a multiple of 4, 8, and 12 Dirac cones for n = 2, 4, and 6, respectively. We show that these anomalous states are physically realized on the surface of new classes of topological crystalline insulators, normal to the rotation axis. Moreover, these topological crystalline insulators support n gapless one-dimensional helical mode on the otherwise fully gapped side surface, connecting the anomalous two-dimensional states on the top and bottom surfaces. The presence of these helical modes enables a new quantum device made from a topological crystalline insulator nanorod, a "helical nanorod," which has a quantized longitudinal conductance of ne2/h.