The diverse series of transition metal dichalcogenide (TMDC) materials has been employed in various optoelectronic applications, such as photodetectors, light‐emitting diodes, and lasers. Typically, the detection or emission range of optoelectronic devices is unique to the bandgap of the active material. Therefore, to improve the capability of these devices, extensive efforts have been devoted to tune the bandgap, such as gating, strain, and dielectric engineering. However, the controllability of these methods is severely limited (typically ≈0.1 eV). In contrast, alloying TMDCs is an effective approach that yields a composition‐dependent bandgap and enables light emissions over a wide range. In this study, a color‐tunable light‐emitting device using compositionally graded TMDC alloys is fabricated. The monolayer WS2/WSe2 alloy grown by chemical vapor deposition shows a spatial gradient in the light‐emission energy, which varies from 2.1 to 1.7 eV. This alloy is incorporated in an electrolyte‐based light‐emitting device structure that can tune the recombination zone laterally. Thus, a continuous and reversible color‐tunable light‐emitting device is successfully fabricated by controlling the light‐emitting positions. The results provide a new approach for exploring monolayer semiconductor‐based broadband optical applications.

To maximize the potential of transition-metal dichalcogenides (TMDCs) in device applications, the development of a sophisticated technique for stable and highly efficient carrier doping is critical. Here, we report the...

In-plane heterostructures of transition metal dichalcogenides (TMDCs) have attracted much attention for high-performance electronic and optoelectronic devices. To date, mainly monolayer-based in-plane heterostructures have been prepared by chemical vapor deposition (CVD), and their optical and electrical properties have been investigated. However, the low dielectric properties of monolayers prevent the generation of high concentrations of thermally excited carriers from doped impurities. To solve this issue, multilayer TMDCs are a promising component for various electronic devices due to the availability of degenerate semiconductors. Here, we report the fabrication and transport properties of multilayer TMDC-based in-plane heterostructures. The multilayer in-plane heterostructures are formed through CVD growth of multilayer MoS2 from the edges of mechanically exfoliated multilayer flakes of WSe2 or Nb x Mo1–x S2. In addition to the in-plane heterostructures, we also confirmed the vertical growth of MoS2 on the exfoliated flakes. For the WSe2/MoS2 sample, an abrupt composition change is confirmed by cross-sectional high-angle annular dark-field scanning transmission electron microscopy. Electrical transport measurements reveal that a tunneling current flows at the Nb x Mo1–x S2/MoS2 in-plane heterointerface, and the band alignment is changed from a staggered gap to a broken gap by electrostatic electron doping of MoS2. The formation of a staggered gap band alignment of Nb x Mo1–x S2/MoS2 is also supported by first-principles calculations.

Water confined inside nanopores exhibits unusual static and dynamic properties that depend on the pore size, pore topology, and hydrophobicity and roughness of the pore walls. The properties also depend on the geometrical shape of the pore cross sections. Here, we investigated water inside distorted single-wall carbon nanotubes (SWCNTs) by means of classical molecular dynamics calculations, over a temperature range of 100–350 K. SWCNTs, which provide ideal one-dimensional cylindrical pores with atomically smooth nonpolar walls, were uniaxially compressed in a direction perpendicular to the SWCNT axes with a deformation ratio γ up to 60%, where γ represents the ratio of deformation amount to the initial SWCNT diameter D. With increasing γ in an SWCNT with D = 1.24 nm, a hexagonal ice nanotube was converted to the liquid state with high water mobility down to 200 K and then to a new form of ice, ice nanoribbon, consisting of four ferroelectric water chains. In an SWCNT with D = 1.51 nm, on the other hand, the water was converted to an ice nanoribbon with five ferroelectric water chains from the liquid state. It was demonstrated that the application of uniaxial pressure is a useful technique to control water properties, such as dielectricity, mobilities, and structures.

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