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Ferroelectric engineered pn doping in two-dimensional (2D) semiconductors hold essential promise in realizing customized functional devices in a reconfigurable manner. Here, we report the successful pn doping in molybdenum disulfide (MoS 2 ) optoelectronic device by local patterned ferroelectric polarization, and its configuration into lateral diode and npn bipolar phototransistors for photodetection from such a versatile playground. The lateral pn diode formed in this way manifests efficient self-powered detection by separating ~12% photo-generated electrons and holes. When polarized as bipolar phototransistor, the device is customized with a gain ~1000 by its transistor action, reaching the responsivity ~12 A W −1 and detectivity over 10 13 Jones while keeping a fast response speed within 20 μs. A promising pathway toward high performance optoelectronics is thus opened up based on local ferroelectric polarization coupled 2D semiconductors. Photodetectors based on two dimensional (2D) materials still suffer from low performance. Here, the authors tackle this issue by introducing a reconfigurable design enabled by locally tuning the doping of a 2D molybdenum disulfide film through the polarization of an underlying ferroelectric material.

As the prevailing non-volatile memory (NVM), flash memory offers mass data storage at high integration density and low cost. However, due to the ‘speed-retention-endurance’ dilemma, their typical speed is limited to ~microseconds to milliseconds for program and erase operations, restricting their application in scenarios with high-speed data throughput. Here, by adopting metallic 1T-Li x MoS 2 as edge contact, we show that ultrafast (10–100 ns) and robust (endurance>10 6 cycles, retention>10 years) memory operation can be simultaneously achieved in a two-dimensional van der Waals heterostructure flash memory with 2H-MoS 2 as semiconductor channel. We attribute the superior performance to the gate tunable Schottky barrier at the edge contact, which can facilitate hot carrier injection to the semiconductor channel and subsequent tunneling when compared to a conventional top contact with high density of defects at the metal interface. Our results suggest that contact engineering can become a strategy to further improve the performance of 2D flash memory devices and meet the increasing demands of high speed and reliable data storage. The speed-retention-endurance trade-off usually limits the performance of flash memory devices. Here, the authors report the realization of van der Waals flash memory cells based on 2H-MoS 2 semiconducting channels with phase-engineered 1T-Li x MoS 2 edge contacts, showing program/erasing speed of ~10/100 ns, endurance of >10 6 cycles and expected retention lifetime of >10 years.

ZnO nanostructure‐based photodetectors have a wide applications in many aspects, however, the response range of which are mainly restricted in the UV region dictated by its bandgap. Herein, UV–vis–NIR sensitive ZnO photodetectors consisting of ZnO nanowires (NW) array/PbS quantum dots (QDs) heterostructures are fabricated through modified electrospining method and an exchanging process. Besides wider response region compared to pure ZnO NWs based photodetectors, the heterostructures based photodetectors have faster response and recovery speed in UV range. Moreover, such photodetectors demonstrate good flexibility as well, which maintain almost constant performances under extreme (up to 180°) and repeat (up to 200 cycles) bending conditions in UV–vis–NIR range. Finally, this strategy is further verified on other kinds of 1D nanowires and 0D QDs, and similar enhancement on the performance of corresponding photodetecetors can be acquired, evidencing the universality of this strategy. UV–vis–NIR photodetector based on electrospun ZnO nanowire array and PbS quantum dots (QDs) thin film heterostructure is fabricated. This heterostructure photodetector exhibits an enhanced response speed and maintains its photoresponse performance via 200 cycles bending. This electrospinning and ligand exchange strategies open up possibilities for UV‐Vis‐NIR and flexible photodetector in optoelectronic circuitry.

The hardware design of supervised learning (SL) in spiking neural network (SNN) prefers 3-terminal memristive synapses, where the third terminal is used to impose supervise signals. In this work we address this demand by fabricating graphene transistor gated through organic ferroelectrics of polyvinylidene fluoride. Through gate tuning not only is the nonvolatile and continuous change of graphene channel conductance demonstrated, but also the transition between electron-dominated and hole-dominated transport. By exploiting the adjustable bipolar characteristic, the graphene–ferroelectric transistor can be electrically reconfigured as potentiative or depressive synapse and in this way complementary synapses are realized. The complementary synapse and neuron circuit is then constructed to execute remote supervise method (ReSuMe) of SNN, and quick convergence to successful learning is found through network-level simulation when applying to a SL task of classifying 3 × 3-pixel images. The presented design of graphene–ferroelectric transistor-based complementary synapses and quantitative simulation may indicate a potential approach to hardware implementation of SL in SNN.

Grain boundaries (GBs) in insulating crystal films generally create lattice reconstruction and excess mid-gap states, which may form the transport pathways of charge carriers and lead to serious degradation of insulating properties. Here, we reveal the inert electrical behaviors of GBs in polycrystalline inorganic molecular dielectric film attributed to its special van der Waals structure. Temperature-dependent electrical measurements and first-principles calculations uncovered that such GBs are free of mid-gap states, which explains the unexpectedly low leakage current of Sb 2 O 3 polycrystalline thin film. Through systematic measurements by conductive atomic force microscopy, we further verify the undistinguishable electrical behaviors within grains and at GBs of the polycrystalline film. Our findings may lay a solid foundation for the applications of inorganic molecular film as a compatible gate dielectric in advanced two-dimensional devices. The authors report that the grain boundary of Sb 2 O 3 molecular films is electrically inert, ensuring high electrical insulation and offering a reliable gate dielectric material choice for next-generation 2D electronics.

Local phase transition in transition metal dichalcogenides (TMDCs) by lithium intercalation enables the fabrication of high‐quality contact interfaces in two‐dimensional (2D) electronic devices. However, controlling the intercalation of lithium is hitherto challenging in vertically stacked van der Waals heterostructures (vdWHs) due to the random diffusion of lithium ions in the hetero‐interface, which hinders their application for contact engineering of 2D vdWHs devices. Herein, a strategy to restrict the lithium intercalation pathway in vdWHs is developed by using surface‐permeation assisted intercalation while sealing all edges, based on which a high‐performance edge‐contact MoS2 vdWHs floating‐gate transistor is demonstrated. Our method avoids intercalation from edges that are prone to be random but intentionally promotes lithium intercalation from the top surface. The derived MoS2 floating‐gate transistor exhibits improved interface quality and significantly reduced subthreshold swing (SS) from >600 to 100 mV dec–1. In addition, ultrafast program/erase performance together with well‐distinguished 32 memory states are demonstrated, making it a promising candidate for low‐power artificial synapses. The study on controlling the lithium intercalation pathways in 2D vdWHs offers a viable route toward high‐performance 2D electronics for memory and neuromorphic computing purposes. A surface‐permeation driven lithium intercalation pathway was proposed to finely control the fabrication of phase engineered edge contact to 2D vdW heterostructure compromising MoS2/hBN/graphene, enabling the development of an ultrafast and multi‐bit memory device, offering promising potential as energy‐efficient artificial synapses for neuromorphic computing applications.

Analyzing sizes of DNA via electrophoresis using a gel has played an important role in the recent, rapid progress of biology and biotechnology. Although analyzing DNA over a wide range of sizes in a short time is desired, no existing electrophoresis methods have been able to fully satisfy these two requirements. Here we propose a novel method using a rigid 3D network structure composed of solid nanowires within a microchannel. This rigid network structure enables analysis of DNA under applied DC electric fields for a large DNA size range (100 bp–166 kbp) within 13 s, which are much wider and faster conditions than those of any existing methods. The network density is readily varied for the targeted DNA size range by tailoring the number of cycles of the nanowire growth only at the desired spatial position within the microchannel. The rigid dense 3D network structure with spatial density control plays an important role in determining the capability for analyzing DNA. Since the present method allows the spatial location and density of the nanostructure within the microchannels to be defined, this unique controllability offers a new strategy to develop an analytical method not only for DNA but also for other biological molecules.

Separation and analysis of biomolecules represent crucial processes for biological and biomedical engineering development; however, separation resolution and speed for biomolecules analysis still require improvements. To achieve separation and analysis of biomolecules in a short time, the use of highly-ordered nanostructures fabricated by top-down or bottom-up approaches have been proposed. Here, we reported on the use of three-dimensional (3D) nanowire structures embedded in microchannels fabricated by a bottom-up approach for ultrafast separation of small biomolecules, such as DNA, protein and RNA molecules. The 3D nanowire structures could analyze a mixture of DNA molecules (50–1000 bp) within 50 s, a mixture of protein molecules (20–340 kDa) within 5 s and a mixture of RNA molecules (100–1000 bases) within 25 s. And, we could observe the electrophoretic mobility difference of biomolecules as a function of molecular size in the 3D nanowire structures. Since the present methodology allows users to control the pore size of sieving materials by varying the number of cycles for nanowire growth, the 3D nanowire structures have a good potential for use as alternatives for other sieving materials.

Controlling the post-growth assembly of nanowires is an important challenge in the development of functional bottom-up devices. Although various methods have been developed for the controlled assembly of nanowires, it is still a challenging issue to align selectively heterogeneous nanowires at desired spatial positions on the substrate. Here we report a size selective deposition and sequential alignment of nanowires by utilizing micrometer scale hydrophilic/hydrophobic patterned substrate. Nanowires dispersed within oil were preferentially deposited only at a water/oil interface onto the hydrophilic patterns. The diameter size of deposited nanowires was strongly limited by the width of hydrophilic patterns, exhibiting the nanoscale size selectivity of nanowires deposited onto micrometer scale hydrophilic patterns. Such size selectivity was due to the nanoscale height variation of a water layer formed onto the micrometer scale hydrophilic patterns. We successfully demonstrated the sequential alignment of different sized nanowires on the same substrate by applying this size selective phenomenon.