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The novel ternary 2D material Bi2O2Se exhibits numerous unique properties in the optical discipline due to its distinctive structure, rendering it of significant research importance and application potential in the domains of new‐generation microelectronics, optoelectronic sensors, and multidimensional optical recognition. However, the optical anisotropy and multidimensional angular resolution of Bi2O2Se have yet to be investigated under the condition of 3D spatial variation of incidence angle. Herein, the spatial optical sensing of the few‐layer Bi2O2Se is investigated under 3D spatially varying incidence conditions using a combination of polarized Raman spectroscopy and multidimensional angle‐resolved spectroscopy. By manipulating the incident angle conditions and adjusting the sample placement angle, a comprehensive optical characterization of materials from diverse spatial orientations is conducted. It is observed that few‐layer Bi2O2Se exhibits a systematically transformed multidimensional spatial photoresponse within visible and near‐infrared wavelengths. This demonstrates the capability of Bi2O2Se as photosensitive semiconductors for 3D stereo optical detection. Furthermore, finite difference time domain simulations reveal that the spatial optical anisotropy of few‐layer Bi2O2Se can be manifested under 3D variable‐angle incidence conditions. The work serves as a crucial guide for the future of Bi2O2Se in anisotropic integrated optics applications, based on polarization‐based chiral recognition. [ABSTRACT FROM AUTHOR]

The microscale structural phase transition in TMDs from 2H to 1T or 1T′ phases offers a distinct approach for modulating the electronic properties of these materials. Although phase engineering for contacts has been partially investigated, the effect of embedding 1T domains in the semiconductor channel on electronic transport has rarely been studied. Here, we investigate the electronic performance of few-layer MoS2 FETs with a local 1T structural phase transition. Through a mild oxygen plasma treatment, we successfully incorporated the 1T phase into the 2H-MoS2 host and observed a significant improvement in the electron mobility of the MoS2 FETs. On the contact side, the local 1T domain serves as a conductive bridge connecting the Au electrode and MoS2 channel, which substantially improves the carrier-injection efficiency. On the channel side, 1T embedded 2H-MoS2 can effectively tailor the electronic structure of the MoS2 channel, significantly increasing channel conductivity. Compared with that before the oxygen plasma treatment, the MoS2 FET demonstrated a higher maximum electron mobility of about two orders of magnitude (up to 237 cm2 V−1 s−1). This study could further promote the development of advanced two-dimensional electronic devices with improved performances. [ABSTRACT FROM AUTHOR]

Exhaustive research of phase engineering of two-dimensional molybdenum disulfide (2D-MoS2) is currently ongoing to develop numerous applications, including optoelectronic devices, spintronics, and new platforms for the study of unconventional quantum phenomena. Therefore, it is urgently needed to achieve phase-controlled synthesis of MoS2 with a high quality and large area. However, the metallic phase MoS2 (1T-MoS2) synthesized by conventional chemical vapor deposition (CVD) is randomly distributed in the semiconductor phase (2H-MoS2) domain, and the position-controlled synthesis of the phase is not achieved. In this study, we achieved the controlled synthesis of the 1T-MoS2 domain in the 2H main phase. Salt-assisted CVD was used to induce V-atom doping at the right time by controlling the concentration of vanadium ions. The synthesis benefitted from 1D vapor–liquid–solid (VLS) growth and 2D vapor–solid (VS) edge expansion. The results of the growth controlled by regulating the NaCl concentration showed that the 1T phase was located at the three vertex domains of the MoS2 triangle. The distribution domains of 1T phase MoS2 can be confirmed by Raman mapping, X-ray photoelectron spectroscopy, and transmission electron microscopy. Furthermore, we calculated the doping rate of V atoms in VLS and VS modes based on the two-dimensional diffusion model and observed that the doping rate of V atoms in the VLS mode was approximately three times higher than that in the VS mode, which was consistent with the experimental results. The controllable phase-domain synthesis of 2D-MoS2 is beneficial to the preparation of nano-electronic devices and provides a platform for the study of physicochemical properties. [ABSTRACT FROM AUTHOR]

The photoelectronic properties of SnS2 flakes have been widely studied due to the abundance and environmentally friendly qualities of this material. However, the defects and residual molecules adsorbed on the SnS2 surface can have a negative influence on the photoelectronic current and photo-response time. In this paper we examine the effects of these two factors on the photoelectronic currents of SnS2 flakes. Defects on a single crystal SnS2 surface are fabricated using hydrogen and oxygen plasma and are characterized by atomic force microscopy, confocal micro-Raman spectroscopy and photoluminescence spectroscopy. Doping by oxygen plasma can be demonstrated by x-ray photoelectron spectroscopy. Both the photoelectronic current and the switching speed (on and off times) are reduced after hydrogen plasma treatment. However, oxygen plasma has two effects on SnS2 thin film transistors. First, oxygen plasma can remove the residual molecules within a short irradiation time. In this case, the photoelectronic current of SnS2 treated with oxygen plasma is enhanced several times. Second, with a longer treatment time oxygen plasma induces many defects and doping on the SnS2 flake surface, as reflected in the reduced photoelectronic current and switching speed. Results of this work have significant practical applications for photoelectronic detection with SnS2 flakes. [ABSTRACT FROM AUTHOR]

The role of interfaces in facilitating the growth of conventional 1D nanostructures is well established. Apparently, the presence of interfaces is also decisive in the growth of 2D transition metal dichalcogenides, but their role remains ambiguous. Here, we show that the molten Na–Nb–O liquid precursor would create microscale vapor–liquid and liquid–solid interfaces, which determine the nucleation and growth of large single-crystal monolayer 2D metallic NbS2 by vapor–liquid–solid (VLS) method. We discover that reaction and growth are separated at the vapor–liquid interface and the liquid–solid interface, respectively, due to the insolubility between S and the liquid precursor. The vapor–liquid interface reaction reduces the concentration of NbSx monomers in droplets, thus effectively controlling the nucleation density. The liquid–solid interface lowers the diffusion barrier of NbS2 monomers, which increases the growth rate. We establish a 2D diffusion model and calculate and conclude that the growth rate in VLS mode is approximately 8 times that in vapor–solid (VS) mode, which is consistent with our experimental results. This finding reveals that two interfaces are the determining factors that control the nucleation and growth of large NbS2 single crystals, which will likely contribute to the development of the wafer-scale growth of 2D materials for further device applications. [ABSTRACT FROM AUTHOR]