Prominently enhanced luminescence from a continuous monolayer of transition metal dichalcogenide on all-dielectric metasurfaces.

2D materials such as transition metal dichalcogenides (TMDCs) are a new class of atomic-layer materials possessing optical and electric properties that significantly depend on the number of layers. Electronic transitions can be manipulated in artificial resonant electromagnetic (EM) fields using metasurfaces and other designed nanostructures. Here, we demonstrate prominently resonant enhancement in the photoluminescence (PL) of atomic monolayer, WS, doped with a small quantity of Mo.

Low Dark Current Operation in InAs/GaAs(111)A Infrared Photodetectors: Role of Misfit Dislocations at the Interface.

We demonstrate an extended short-wave infrared (-SWIR) photodetector composed of an InAs/GaAs(111)A heterostructure with interface misfit dislocations. The layer structure of the photodetector consists simply of an -InAs optical absorption layer directly grown with a thin undoped-GaAs spacer layer on -GaAs by molecular beam epitaxy. The lattice mismatch was abruptly relaxed by forming a misfit dislocation network at the initial stage of the InAs growth.

Highly Efficient Deposition of Centimeter-Scale MoS Monolayer Film on Dragontrail Glass with Large Single-Crystalline Domains.

Highly efficient growth of a centimeter-scale MoS monolayer film by oxide scale sublimation chemical vapor deposition (OSSCVD) in a time as short as 60 s is reported. Benefiting from the superior catalytic ability of Dragontrail glass (DT-glass) substrate and the controlled large vapor supersaturation of the molybdenum source, the ultrafast deposition of MoS is realized with maintaining large-sized single-crystalline domains over 20 µm at maximum in the film. It is comparable to those reported for MoS grown in tens of minutes and even hours.

Oxide Scale Sublimation Chemical Vapor Deposition for Controllable Growth of Monolayer MoS Crystals.

A newly developed oxide scale sublimation chemical vapor deposition (OSSCVD) technique for 2D MoS growth is reported. Gaseous MoO , which is supplied separately from H S, can be generated in situ by flowing O over Mo metal with oxidation and sublimation processes. In this method, particularly, controllably and abruptly modulating the supply of MoO is achievable by precisely tuning O flow.

Tunable Doping of Rhenium and Vanadium into Transition Metal Dichalcogenides for Two-Dimensional Electronics.

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) with unique electrical properties are fascinating materials used for future electronics. However, the strong Fermi level pinning effect at the interface of TMDCs and metal electrodes always leads to high contact resistance, which seriously hinders their application in 2D electronics. One effective way to overcome this is to use metallic TMDCs or transferred metal electrodes as van der Waals (vdW) contacts.

Strain relaxation in InAs heteroepitaxy on lattice-mismatched substrates.

Strain relaxation processes in InAs heteroepitaxy have been studied. While InAs grows in a layer-by-layer mode on lattice-mismatched substrates of GaAs(111)A, Si(111), and GaSb(111)A, the strain relaxation process strongly depends on the lattice mismatch. The density of threading defects in the InAs film increases with lattice mismatch.

Double-Sided Nonalloyed Ohmic Contacts to Si-doped GaAs for Plasmoelectronic Devices.

There is increasing demand for the ability to form ohmic contacts without lossy intermediate layers on both the top and bottom sides of metal-semiconductor-metal plasmoelectronic devices such as quantum cascade lasers and metasurface photodetectors. Although highly Si-doped n-GaAs surfaces can allow an ohmic contact without alloying, conditions for realizing nonalloyed ohmic contacts to other n-GaAs surfaces, originally buried inside but exposed by removing the substrate, have yet to be studied. We discovered that nonalloyed ohmic contacts to initially buried surfaces with a practically low contact resistivity down to 77 K can be realized by fulfilling certain requirements, specifically keeping the Si-doping concentration within a narrow range of 7.

Strain Relaxation in GaSb/GaAs(111)A Heteroepitaxy Using Thin InAs Interlayers.

We have systematically studied the strain relaxation processes in GaSb heteroepitaxy on GaAs(111)A using thin InAs interlayers. The growth with 1 ML- and 2 ML-InAs leads to formation of an InAsSb-like layer, which induces tensile strain in GaSb films, whereas the GaSb films grown with thicker InAs layers (≥3 ML) are under compressive strain. As the InAs thickness is increased above 5 ML, the insertion of the InAs layer becomes less effective in the strain relaxation, leaving residual strain in GaSb films.

Wafer-scale and deterministic patterned growth of monolayer MoSvia vapor-liquid-solid method.

Vapor transportation is the core process in growing transition-metal dichalcogenides (TMDCs) by chemical vapor deposition (CVD). One inevitable problem is the spatial inhomogeneity of vapors. The non-stoichiometric supply of transition-metal precursors and chalcogens leads to poor control in the products' location, morphology, crystallinity, uniformity and batch to batch reproducibility.

Quantum key distribution over 120 km using ultrahigh purity single-photon source and superconducting single-photon detectors.

Advances in single-photon sources (SPSs) and single-photon detectors (SPDs) promise unique applications in the field of quantum information technology. In this paper, we report long-distance quantum key distribution (QKD) by using state-of-the-art devices: a quantum-dot SPS (QD SPS) emitting a photon in the telecom band of 1.5 μm and a superconducting nanowire SPD (SNSPD).

Direct visualization of the N impurity state in dilute GaNAs using scanning tunneling microscopy.

The interaction between nitrogen (N) impurity states in III-V compounds plays a key role in controlling optoelectronic properties of the host materials. Here, we use scanning tunneling microscopy to characterize the spatial distribution and electronic properties of N impurity states in dilute GaNAs. We demonstrated that the N impurity states can be directly visualized by taking empty state current images using the multipass scanning method.

Visible-light photodecomposition of acetaldehyde by TiO2-coated gold nanocages: plasmon-mediated hot electron transport via defect states.

Skeletal gold nanocages (Au NCs) are synthesized and coated with TiO2 layers (TiO2-Au NCs). The TiO2-Au NCs exhibit enhanced photodecomposition activity toward acetaldehyde under visible light (>400 nm) illumination because hot electrons are generated over the Au NCs by local surface plasmon resonance (LSPR) and efficiently transported across the metal/semiconductor interface via the defect states of TiO2.

Role of glutamine-169 in the substrate recognition of human aminopeptidase B.

Background: Aminopeptidase B (EC 3.4.11.

Experimental study of near-field light collection efficiency of aperture fiber probe at near-infrared wavelengths.

We examined the near-field collection efficiency of near-infrared radiation for an aperture probe. We used InAs quantum dots as ideal point light sources with emission wavelengths ranging from 1.1 to 1.

Cathodoluminescence study of AlGaAs/GaAs multilayers grown on ridge-type triangles on GaAs (111)A substrates.

We have studied the cathodoluminescence of AlxGa1-xAs/GaAs multilayers grown on ridge-type triangles by molecular beam epitaxy. The compositional variation of Al, as well as the distribution of impurity and/or defect, was revealed by variations in the cathodoluminescence spectra and images. The Al composition in an AlxGa1-xAs layer was highest in the (111)A facet and decreased in the order (100), (411)A, (111)-delta and (110) facets.