The coupling effect characterization for van der Waals structures based on transition metal dichalcogenides

van der Waals(vdW)heterostructures based on two-dimensional(2D)materials holding design-by-demand features offer astonishing opportunities to construct novel electronics and optoelectronics devices due to the vdW force interaction between their stacked components.At the atomically thin confinement,vdW heterostructure not only exhibits unprecedented properties as an entire counterpart,but also provides unique platforms to manipulate the vdW interfacial behaviors.Therefore,developing characterization techniques to comprehensively understand the coupling effect on structure-property-performance relationship of vdW heterostructures is crucial for fundamental science and practical applications.Here,we focus on the most widely studied 2D semiconductor transition metal dichalcogenides(TMDCs)and systematically review significant advances in characterizing the material and interfacial coupling effect of the related vdW heterostructures.Specially,we will discuss microscopy techniques for unveiling the structure-property relationship of vdW heterostructures and optical spectroscopy measurements for analyzing vdW interfacial coupling effect.Finally,we address some promising strategies to optimize characterization technologies for resolving vdW heterostructures,including coupling multiple characterization technologies,improving temporal and spatial resolution,developing fast,efficient,and non-destructive techniques and introducing artificial intelligence.

Synergistic-engineered van der Waals photodiodes with high efficiency

Van der Waals(vdW)heterostructures based on two-dimensional transitionmetal dichalcogenides have provided unprecedented opportunities for photovoltaic detectors owing to their strong light-matter interaction and ultrafast interfacial charge transfer.Despite continued advancement,insufficient control of photocarrier behaviors still limits the external quantum efficiency(EQE)and operation speed of such detectors.Here,we propose a synergistic strategy of contact-configuration design and thickness-modulation to construct high-performance vdW photodiodes based on the typical type II heterostructure(MoS2/WSe2).Through integrating three contact architectures into one device to exclude other factors,we solid the superiority of designed 1L-MoS2/WSe2/graphene heterostructures incorporating efficient photocarrier collection and gate modulation.Together with leveraging the layer-numberdependent properties of WSe2,we observe the critical thickness of WSe2(11 layers)for the highest EQE,which verifies the thickness-dependent competition between photocarrier generation,dissociation,and collection.Finally,we demonstrate the synergistic-engineered vdW heterostructure can trigger record-high EQE(61%)and manifest ultrafast photoresponse(4.1μs)at the atomically thin limit(8 nm).The proposed strategy enables architecture-design and thickness-engineering to unlock the potential to realize high-performance optoelectronic devices.

Record-high saturation current in end-bond contacted monolayer MoS_(2) transistors

Monolayer two-dimensional(2D)semiconductors are emerging as top candidates for the channels of the future chip industry due to their atomically thin body and superior immunity to short channel effect.However,the low saturation current caused by the high contact resistance(R_(c))in monolayer MoS2 field-effect transistors(FETs)limits ultimate electrical performance at scaled contact lengths,which seriously hinders application of monolayer MoS_(2 )transistors.Here we present a scalable strategy with a clean end-bond contact scheme that leads to size-independent electrodes and ultralow contact resistance of 2.5 kΩ·μm to achieve record high performances of saturation current density of 730μA·μm^(-1)at 300 K and 960μA·μm^(-1)at 6 K.Our end-bond contact strategy in monolayer MoS2 FETs enables the great potential for atomically thin integrated circuitry.