Defects play an indispensable role in tuning the optical properties of twodimensional materials. Herein, we study the influence of defects on the photoluminescence and resonance Raman spectra of as-grown monolayer (1L) WS 2 . Increasing the density of defects significantly lowers the excitonic binding energy by up to 110 meV. These defect-modified excitonic binding energies in 1L-WS 2 strongly mediate the Raman resonance condition, resulting in unexpected Raman intensity variations in the LA(M), 2LA(M), and A 1 ′(Γ) phonon modes. The sample with the highest density of defects exhibits an almost temperature-independent resonance in different Raman modes at low temperature, whereas the samples with low densities of defects exhibit a clear resonance with decreasing temperature. This study will further increase our understanding of the role of defects in resonance Raman spectroscopy and of the phonon−exciton interaction in 1L-WS 2 .

Vertical heterostructures of two-dimensional (2D) transition metal dichalcogenides (TMDCs) provide a prospective foreground for practical applications via combining novel physical characteristics that are distinguished from those of traditional counterparts. Here, we report the position-selective growth of 2D WS 2 -based vertical heterostructures, including WS 2 /MoS 2 , WS 2 /MoS 2 -Mo 0.42 W 0.58 S 2 , WS 2 /MoS 2 -Mo 1−x W x S 2 (0.4 ≤ x ≤ 0.85), and WS 2 /Mo 1−x W x S 2 (0 ≤ x ≤ 0.76), with the WS 2 monolayer as the top layer by a one-step chemical vapor deposition (CVD) method. Systematical Raman and photoluminescence (PL) characterizations corroborate that position-dependent vertical heterostructures exhibit a significant relationship between structural/optical characteristics and compositions. A possible growth mechanism of various 2D WS 2 -based heterostructures at different deposition regions is discussed based on the variation of metallic atoms along the gas flow direction. The current work supplies a promising and efficient strategy to fabricate complex heterostructures composed of various TMDCs, which is a crucial step to develop functional optoelectronic applications.

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Two‐dimensional (2D) magnetic semiconductors are considered to have great application prospects in spintronic logic devices, memory devices, and photodetectors, due to their unique structures and outstanding physical properties in 2D confinement. Understanding the influence of magnetism on optical/optoelectronic properties of 2D magnetic semiconductors is a significant issue for constructing multifunctional electronic devices and implementing sophisticated functions. Herein, the influence of spin ordering and magnons on the optical/optoelectronic properties of 2D magnetic semiconductor α ‐MnSe synthesized by space‐confined chemical vapor deposition (CVD) is explored systematically. The spin‐ordering‐induced magnetic phase transition triggers temperature‐dependent photoluminescence spectra to produce a huge transition at Néel temperature ( T N ≈ 160 K). The magnons‐ and defects‐induced emissions are the primary luminescence path below T N and direct internal 4 a T 1g → 6 A 1g transition‐induced emissions are the main luminescence path above T N . Additionally, the magnons and defect structures endow 2D α ‐MnSe with a broadband luminescence from 550 to 880 nm, and an ultraviolet–near‐infrared photoresponse from 365 to 808 nm. Moreover, the device also demonstrates improved photodetection performance at 80 K, possibly influenced by spin ordering and trap states associated with defects. These above findings indicate that 2D magnetic semiconductor α ‐MnSe provides an excellent platform for magneto‐optical and magneto‐optoelectronic research.

In article number 1903446, Kenjiro Fukuda, Takao Someya, and co‐workers demonstrate a simple fabrication approach for porous nanomesh‐type elastic conductors consisting of Ag nanowires and polyurethane nanofibers. The conductors simultaneously achieve high conductivity (9190 S cm−1), high stretchability (310%), and good durability. Without any adhesive gel/tape, the conductors can be utilized as skin‐attachable strain sensors and dry biosignal‐sensing electrodes.