Few-layer transition metal dichalcogenides (TMDs) and their combination as van der Waals heterostructures provide a promising platform for high-performance optoelectronic devices. However, the ultrathin thickness of TMD flakes limits efficient light trapping and absorption, which triggers the hybrid construction with optical resonant cavities for enhanced light absorption. The optical structure enriched photodetectors can also be wavelength-and polarization-sensitive but require complicated fabrication. Herein, a new-type TMD-based photodetector embedded with nanoslits is proposed to enhance light trapping. Taking ReS 2 as an example, strong anisotropic Mie-type optical responses arising from the intrinsic in-plane anisotropy and nanoslit-enhanced anisotropy are discovered. Owing to the nanoslit-enhanced optical resonances and band engineering, excellent photodetection performances are demonstrated with high responsivity of 27 A W −1 and short rise/decay times of 3.7/3.7 ms. More importantly, through controlling the angle between the nanoslit orientation and the polarization direction to excite different resonant modes, polarization-sensitive photodetectors with anisotropy ratios from 5.9 to 12.6 can be achieved, representing one of the most polarization-sensitive TMD-based photodetectors. The depth and orientation of nanoslits are demonstrated crucial for optimizing the anisotropy ratio. The findings bring an effective scheme to construct high-performance and polarization-sensitive photodetectors.
A van der Waals heterojunction photodetector has been constructed by vertically stacking a TaIrTe4 flake, a 2D type-II Weyl semimetal, and a WSe2 flake, a typical isotropic 2D semiconductor. Interestingly, the device exhibits a switchable operating mode depending on the direction of the voltage bias. Specifically, under a source-drain bias of −1 V, the device operates in a photovoltaic mode, featuring rapid response rate. Its response/recovery time is down to 22.5/25.1 ms, which is approximately one order of magnitude shorter than that of a pristine WSe2 photodetector (320/360 ms). In contrast, under a source-drain bias of +1 V, the device operates in a photoconductive mode with high photogain. The optimized responsivity reaches 9.1 A/W, and the corresponding external quantum efficiency and detectivity reach 2776% and 3.09 × 1012 Jones, respectively. Furthermore, the effective wavelength range of the TaIrTe4–WSe2 device has been extended to the long-wavelength region as compared to a WSe2 device. Beyond these, by virtue of the highly anisotropic crystal structure of TaIrTe4, the hybrid device exhibits polarized photosensitivity. Its anisotropy ratio reaches 1.72 (1.75) under a voltage bias of +1 (−1 V). On the whole, this research work provides a paradigm for the design and implementation of 2D materials based multifunctional optoelectronic devices.
High‐index all‐dielectric resonators have been developed into an important platform for light manipulation at the nanoscale over the past decade. Although they are widely used as 2D materials, transition metal dichalcogenides (TMDCs), as an emerging all‐dielectric material, have also been used to fabricate optical nanoantennas that support multipolar Mie resonances. However, their fabrication depends heavily on electron‐beam lithography (EBL) or focused ion beam (FIB), which is expensive and time‐consuming for practical applications. To address this issue, here, a fast low‐cost method is put forward which combines polystyrene (PS) nanospheres with physical vapor deposition by electron‐beam evaporation and magnetron sputtering to fabricate WS2 nanodisks in a mass‐production manner. After annealing, the A‐ and B‐exciton features as well as anapole states are observed in the scattering spectra of WS2 nanodisks. The light scattering anisotropy of individual WS2 nanodisks and spectral tunability of the anapole are studied. In addition, absorption enhancement due to the strong field localization of anapole states in hexagonal WS2 nanodisk arrays is numerically demonstrated. This work manifests that this etching‐free method is promising for fabrication of scalable TMDC nanodisks suitable for practical applications.
The emergence of graphene has opened the prelude of extensive research on 2D layered materials. Especially, the diverse crystal structures and exceptional physical properties of multielement van der Waals semiconductors have provided a brand‐new platform for the implementation of novel optoelectronic devices. In this study, for the first time, the optoelectronic properties of a newly emerged quaternary van der Waals semiconductor, namely silver indium phosphorus sulfide (AgInP2S6), have been systematically investigated. It is revealed that the AgInP2S6 photodetector exhibits a fast response rate with the response/recovery time down to ≈1/2 ms. In addition, the AgInP2S6 device demonstrates stable photoswitching operation even under a high working temperature of up to 160 °C in the ambient environment without using any specific protection means, and the photoswitching characteristic is also well reserved after a 10‐h continuous heating at 150 °C in air. Profiting from the strong immunity to environmental thermal disturbance, a proof‐of‐concept high‐temperature optical communication application is demonstrated. In conclusion, this study provides an intriguing paradigm for the realization of the next‐generation optoelectronic devices against extreme working circumstances, which contributes to further broadening the scope of application of 2D material photodetectors in the upcoming future (e.g., space communication and tracking).
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