Colossal room-temperature non-reciprocal Hall effect.

Non-reciprocal charge transport has gained significant attention due to its potential in exploring quantum symmetry and its promising applications. Traditionally, non-reciprocal transport has been observed in the longitudinal direction, with non-reciprocal resistance being a small fraction of the ohmic resistance. Here we report a transverse non-reciprocal transport phenomenon featuring a quadratic current-voltage characteristic and divergent non-reciprocity, termed the non-reciprocal Hall effect.

Confinement of excited states in two-dimensional, in-plane, quantum heterostructures.

Two-dimensional (2D) semiconductors are promising candidates for optoelectronic application and quantum information processes due to their inherent out-of-plane 2D confinement. In addition, they offer the possibility of achieving low-dimensional in-plane exciton confinement, similar to zero-dimensional quantum dots, with intriguing optical and electronic properties via strain or composition engineering. However, realizing such laterally confined 2D monolayers and systematically controlling size-dependent optical properties remain significant challenges.

Chemical Environment and Structural Variations in High Entropy Oxide Thin Film Probed with Electron Microscopy.

We employ analytical transmission electron microscopy (TEM) to correlate the structural and chemical environment variations within a stacked epitaxial thin film of the high entropy oxide (HEO) MgCoNiCuZnO (J14), with two layers grown at different substrate temperatures (500 and 200 °C) using pulsed laser deposition (PLD). Electron diffraction and atomically resolved STEM imaging reveal the difference in out-of-plane lattice parameters in the stacked thin film, which is further quantified on a larger scale using four-dimensional STEM (4D-STEM). In the layer deposited at a lower temperature, electron energy loss spectroscopy (EELS) mapping indicates drastic changes in the oxidation states and bonding environment for Co ions, and energy-dispersive X-ray spectroscopy (EDX) mapping detects more significant cation deficiency.

High-entropy engineering of the crystal and electronic structures in a Dirac material.

Dirac and Weyl semimetals are a central topic of contemporary condensed matter physics, and the discovery of new compounds with Dirac/Weyl electronic states is crucial to the advancement of topological materials and quantum technologies. Here we show a widely applicable strategy that uses high configuration entropy to engineer relativistic electronic states. We take the AMnSb (A = Ba, Sr, Ca, Eu, and Yb) Dirac material family as an example and demonstrate that mixing of Ba, Sr, Ca, Eu and Yb at the A site generates the compound (BaSrCaEuYb)MnSb (denoted as AMnSb), giving access to a polar structure with a space group that is not present in any of the parent compounds.

Step engineering for nucleation and domain orientation control in WSe epitaxy on c-plane sapphire.

Epitaxial growth of two-dimensional transition metal dichalcogenides on sapphire has emerged as a promising route to wafer-scale single-crystal films. Steps on the sapphire act as sites for transition metal dichalcogenide nucleation and can impart a preferred domain orientation, resulting in a substantial reduction in mirror twins. Here we demonstrate control of both the nucleation site and unidirectional growth direction of WSe on c-plane sapphire by metal-organic chemical vapour deposition.

Role of Bilayer Graphene Microstructure on the Nucleation of WSe Overlayers.

Over the past few years, graphene grown by chemical vapor deposition (CVD) has gained prominence as a template to grow transition metal dichalcogenide (TMD) overlayers. The resulting two-dimensional (2D) TMD/graphene vertical heterostructures are attractive for optoelectronic and energy applications. However, the effects of the microstructural heterogeneities of graphene grown by CVD on the growth of the TMD overlayers are relatively unknown.

Layered Semiconductor CrGaTe with Concurrent Broken Inversion Symmetry and Ferromagnetism: A Bulk Ferrovalley Material Candidate.

The valleytronic state found in group-VI transition-metal dichalcogenides such as MoS has attracted immense interest since its valley degree of freedom could be used as an information carrier. However, valleytronic applications require spontaneous valley polarization. Such an electronic state is predicted to be accessible in a new ferroic family of materials, i.

Al Coordination and Ga Interstitial Stability in a β-(AlGa)O Thin Film.

Alloying AlO with GaO to form β-(AlGa)O opens the door to a large number of new possibilities for the fabrication of devices with tunable properties in many high-performance applications such as optoelectronics, sensing systems, and high-power electronics. Often, the properties of these devices are impacted by defects induced during the growth process. In this work, we uncover the crystal structure of a β-(AlGa)O/β-GaO interface grown by molecular beam epitaxy.

Strong room-temperature bulk nonlinear Hall effect in a spin-valley locked Dirac material.

Nonlinear Hall effect (NLHE) is a new type of Hall effect with wide application prospects. Practical device applications require strong NLHE at room temperature (RT). However, previously reported NLHEs are all low-temperature phenomena except for the surface NLHE of TaIrTe.

Crossover from Ising- to Rashba-type superconductivity in epitaxial BiSe/monolayer NbSe heterostructures.

A topological insulator (TI) interfaced with an s-wave superconductor has been predicted to host topological superconductivity. Although the growth of epitaxial TI films on s-wave superconductors has been achieved by molecular-beam epitaxy, it remains an outstanding challenge for synthesizing atomically thin TI/superconductor heterostructures, which are critical for engineering the topological superconducting phase. Here we used molecular-beam epitaxy to grow BiSe films with a controlled thickness on monolayer NbSe and performed in situ angle-resolved photoemission spectroscopy and ex situ magnetotransport measurements on these heterostructures.

Understanding Signatures of Emergent Magnetism in Topological Insulator/Ferrite Bilayers.

Magnetic insulator-topological insulator heterostructures have been studied in search of chiral edge states via proximity induced magnetism in the topological insulator, but these states have been elusive. We identified MgAl_{0.5}Fe_{1.

Substrate Modification during Chemical Vapor Deposition of hBN on Sapphire.

A comparison of hexagonal boron nitride (hBN) layers grown by chemical vapor deposition on -plane (0001) versus -plane (112̅0) sapphire (α-AlO) substrate is reported. The high deposition temperature (>1200 °C) and hydrogen ambient used for hBN deposition on sapphire substantially alters the -plane sapphire surface chemistry and leaves the top layer(s) oxygen deficient. The resulting surface morphology due to H etching of -plane sapphire is inhomogeneous with increased surface roughness which causes non-uniform residual stress in the deposited hBN film.

Illuminating Invisible Grain Boundaries in Coalesced Single-Orientation WS Monolayer Films.

Engineering atomic-scale defects is crucial for realizing wafer-scale, single-crystalline transition metal dichalcogenide monolayers for electronic devices. However, connecting atomic-scale defects to larger morphologies poses a significant challenge. Using electron microscopy and ReaxFF reactive force field-based molecular dynamics simulations, we provide insights into WS crystal growth mechanisms, providing a direct link between synthetic conditions and microstructure.

Picometer-Precision Atomic Position Tracking through Electron Microscopy.

The modern aberration-corrected scanning transmission electron microscopes (AC-STEM) have successfully achieved direct visualization of atomic columns with sub-angstrom resolution. With this significant progress, advanced image quantification and analysis are still at the early stages. In this work, we present the complete pathway for the metrology of atomic resolution scanning transmission electron microscopy (STEM) images.

Wafer-Scale Epitaxial Growth of Unidirectional WS Monolayers on Sapphire.

Realization of wafer-scale single-crystal films of transition metal dichalcogenides (TMDs) such as WS requires epitaxial growth and coalescence of oriented domains to form a continuous monolayer. The domains must be oriented in the same crystallographic direction on the substrate to inhibit the formation of inversion domain boundaries (IDBs), which are a common feature of layered chalcogenides. Here we demonstrate fully coalesced unidirectional WS monolayers on 2 in.

Monolayer Vanadium-Doped Tungsten Disulfide: A Room-Temperature Dilute Magnetic Semiconductor.

Dilute magnetic semiconductors (DMS), achieved through substitutional doping of spin-polarized transition metals into semiconducting systems, enable experimental modulation of spin dynamics in ways that hold great promise for novel magneto-electric or magneto-optical devices, especially for two-dimensional (2D) systems such as transition metal dichalcogenides that accentuate interactions and activate valley degrees of freedom. Practical applications of 2D magnetism will likely require room-temperature operation, air stability, and (for magnetic semiconductors) the ability to achieve optimal doping levels without dopant aggregation. Here, room-temperature ferromagnetic order obtained in semiconducting vanadium-doped tungsten disulfide monolayers produced by a reliable single-step film sulfidation method across an exceptionally wide range of vanadium concentrations, up to 12 at% with minimal dopant aggregation, is described.

Oxide-Free Three-Dimensional Germanium/Silicon Core-Shell Metalattice Made by High-Pressure Confined Chemical Vapor Deposition.

Metalattices are crystalline arrays of uniform particles in which the period of the crystal is close to some characteristic physical length scale of the material. Here, we explore the synthesis and properties of a germanium metalattice in which the ∼70 nm periodicity of a silica colloidal crystal template is close to the ∼24 nm Bohr exciton radius of the nanocrystalline Ge replica. The problem of Ge surface oxidation can be significant when exploring quantum confinement effects or designing electronically coupled nanostructures because of the high surface area to volume ratio at the nanoscale.

Author Correction: Giant room temperature anomalous Hall effect and tunable topology in a ferromagnetic topological semimetal CoMnAl.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Giant room temperature anomalous Hall effect and tunable topology in a ferromagnetic topological semimetal CoMnAl.

Weyl semimetals exhibit unusual surface states and anomalous transport phenomena. It is hard to manipulate the band structure topology of specific Weyl materials. Topological transport phenomena usually appear at very low temperatures, which sets challenges for applications.

Sputtered SrNbO as a UV-Transparent Conducting Film.

Expanding the application space of transparent electrodes toward the ultraviolet range has been found challenging when utilizing the conventional approach to degenerately dope semiconductors with band gaps larger than ZnO or InO. Here, it is shown that the correlated metal SrNbO with < 1 is ideally suited as a UV-transparent electrode material, enabling UV light-emitting diodes for a wide range of applications from water disinfection to polymer curing. It is demonstrated that SrNbO thin films can be grown by radio frequency (RF) sputtering and that they remain in the perovskite phase despite a sizeable Sr deficiency.