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Three-dimensional monolithic integration of memory devices with logic transistors is a frontier challenge in computer hardware. This integration is essential for augmenting computational power concurrent with enhanced energy efficiency in big data applications such as artificial intelligence. Despite decades of efforts, there remains an urgent need for reliable, compact, fast, energy-efficient and scalable memory devices. Ferroelectric field-effect transistors (FE-FETs) are a promising candidate, but requisite scalability and performance in a back-end-of-line process have proven challenging. Here we present back-end-of-line-compatible FE-FETs using two-dimensional MoS 2 channels and AlScN ferroelectric materials, all grown via wafer-scalable processes. A large array of FE-FETs with memory windows larger than 7.8 V, ON/OFF ratios greater than 10 7 and ON-current density greater than 250 μA um –1 , all at ~80 nm channel length are demonstrated. The FE-FETs show stable retention up to 10 years by extension, and endurance greater than 10 4  cycles in addition to 4-bit pulse-programmable memory features, thereby opening a path towards the three-dimensional heterointegration of a two-dimensional semiconductor memory with silicon complementary metal–oxide–semiconductor logic. A large array of ferroelectric field-effect transistors with record memory windows, ON/OFF ratios and ON-current density is presented at ~80 nm channel length.

Two-dimensional transition metal dichalcogenide nanoribbons are touted as the future extreme device downscaling for advanced logic and memory devices but remain a formidable synthetic challenge. Here, we demonstrate a ledge-directed epitaxy (LDE) of dense arrays of continuous, self-aligned, monolayer and single-crystalline MoS 2 nanoribbons on β-gallium ( iii ) oxide (β-Ga 2 O 3 ) (100) substrates. LDE MoS 2 nanoribbons have spatial uniformity over a long range and transport characteristics on par with those seen in exfoliated benchmarks. Prototype MoS 2 -nanoribbon-based field-effect transistors exhibit high on/off ratios of 10 8 and an averaged room temperature electron mobility of 65 cm 2  V −1  s −1 . The MoS 2 nanoribbons can be readily transferred to arbitrary substrates while the underlying β-Ga 2 O 3 can be reused after mechanical exfoliation. We further demonstrate LDE as a versatile epitaxy platform for the growth of p-type WSe 2 nanoribbons and lateral heterostructures made of p-WSe 2 and n-MoS 2 nanoribbons for futuristic electronics applications. Aligned arrays of single-crystalline monolayer TMD nanoribbons with high aspect ratios, as well as their lateral heterostructures, are realized, with the growth directed by the ledges on the β-Ga 2 O 3 substrate. This approach provides an epitaxy platform for advanced electronics applications of TMD nanoribbons.

Architected materials that actively respond to external stimuli hold tantalizing prospects for applications in energy storage, wearable electronics, and bioengineering. Molybdenum disulfide, an excellent two-dimensional building block, is a promising candidate for lithium-ion battery anode. However, the stacked and brittle two-dimensional layered structure limits its rate capability and electrochemical stability. Here we report the dewetting-induced manufacturing of two-dimensional molybdenum disulfide nanosheets into a three-dimensional foam with a structural hierarchy across seven orders of magnitude. Our molybdenum disulfide foam provides an interpenetrating network for efficient charge transport, rapid ion diffusion, and mechanically resilient and chemically stable support for electrochemical reactions. These features induce a pseudocapacitive energy storage mechanism involving molybdenum redox reactions, confirmed by in-situ X-ray absorption near edge structure. The extraordinary electrochemical performance of molybdenum disulfide foam outperforms most reported molybdenum disulfide-based Lithium-ion battery anodes and state-of-the-art materials. This work opens promising inroads for various applications where special properties arise from hierarchical architecture. The stacked and brittle 2D layered structure of molybdenum disulphide limits its practical application in lithium ion batteries. Here, authors report a dewetting-induced manufacture strategy to create the interpenetrating network and induce the pseudocapacity to improve the electrochemical performance.

Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) represent the ultimate thickness for scaling down channel materials. They provide a tantalizing solution to push the limit of semiconductor technology nodes in the sub-1 nm range. One key challenge with 2D semiconducting TMD channel materials is to achieve large-scale batch growth on insulating substrates of single crystals with spatial homogeneity and compelling electrical properties. Recent studies have claimed the epitaxy growth of wafer-scale, single-crystal 2D TMDs on a c -plane sapphire substrate with deliberately engineered off-cut angles. It has been postulated that exposed step edges break the energy degeneracy of nucleation and thus drive the seamless stitching of mono-oriented flakes. Here we show that a more dominant factor should be considered: in particular, the interaction of 2D TMD grains with the exposed oxygen–aluminium atomic plane establishes an energy-minimized 2D TMD–sapphire configuration. Reconstructing the surfaces of c -plane sapphire substrates to only a single type of atomic plane (plane symmetry) already guarantees the single-crystal epitaxy of monolayer TMDs without the aid of step edges. Electrical results evidence the structural uniformity of the monolayers. Our findings elucidate a long-standing question that curbs the wafer-scale batch epitaxy of 2D TMD single crystals—an important step towards using 2D materials for future electronics. Experiments extended to perovskite materials also support the argument that the interaction with sapphire atomic surfaces is more dominant than step-edge docking. Interaction of two-dimensional transition metal dichalcogenide grains with exposed oxygen–aluminium atomic plane in sapphire is a more dominant factor than step-edge docking in controlling the single-crystal epitaxy of these materials.

The development of membranes that block solutes while allowing rapid water transport is of great importance. The microstructure of the membrane needs to be rationally designed at the molecular level to achieve precise molecular sieving and high water flux simultaneously. We report the design and fabrication of ultrathin, ordered conjugated-polymer-framework (CPF) films with thicknesses down to 1 nm via chemical vapour deposition and their performance as separation membranes. Our CPF membranes inherently have regular rhombic sub-nanometre (10.3 × 3.7 Å) channels, unlike membranes made of carbon nanotubes or graphene, whose separation performance depends on the alignment or stacking of materials. The optimized membrane exhibited a high water/NaCl selectivity of ∼6,900 and water permeance of ∼112 mol m −2  h −1  bar −1 , and salt rejection >99.5% in high-salinity mixed-ion separations driven by osmotic pressure. Molecular dynamics simulations revealed that water molecules quickly and collectively pass through the membrane by forming a continuous three-dimensional network within the hydrophobic channels. The advent of ordered CPF provides a route towards developing carbon-based membranes for precise molecular separation. Carbon nanomaterials such as graphene show intriguing molecular transport properties, but to achieve regular channels over a large area requires perfect sheet alignment. Here, a large-area two-dimensional conjugated-polymer-framework is grown with regular pore distribution, enabling 99.5% salt rejection by forward osmosis.

Two-dimensional (2D) semiconducting monolayers such as transition metal dichalcogenides (TMDs) are promising channel materials to extend Moore’s Law in advanced electronics. Synthetic TMD layers from chemical vapor deposition (CVD) are scalable for fabrication but notorious for their high defect densities. Therefore, innovative endeavors on growth reaction to enhance their quality are urgently needed. Here, we report that the hydroxide W species, an extremely pure vapor phase metal precursor form, is very efficient for sulfurization, leading to about one order of magnitude lower defect density compared to those from conventional CVD methods. The field-effect transistor (FET) devices based on the proposed growth reach a peak electron mobility ~200 cm 2 /Vs (~800 cm 2 /Vs) at room temperature (15 K), comparable to those from exfoliated flakes. The FET device with a channel length of 100 nm displays a high on-state current of ~400 µA/µm, encouraging the industrialization of 2D materials. Chemical vapor deposition enables the scalable production of 2D semiconductors, but the grown materials are usually affected by high defect densities. Here, the authors report a hydroxide vapour phase deposition method to synthesize wafer-scale monolayer WS 2 with reduced defect density and electrical properties comparable to those of exfoliated flakes.

Van der Waals (vdW) integration, in which pre-engineered two-dimensional building blocks are physically assembled together in a chosen sequence through weak vdW interactions, holds promise toward previously unattainable applications. However, when extended to create 3D/3D monoliths, the lack of physical bonding coupled with the inherent rigidity and surface roughness between 3D building blocks makes it challenging for broader implementation of composites, catalysis, and energy applications. Here we demonstrate that electrostatically exfoliated two-dimensional layered materials can be additively manufactured to create complex layouts with selectively engineered composition in both lateral and vertical directions. Subsequent room-temperature dewetting creates non-covalent hinges through folded edges to concurrently interlock and nanostructure the two-dimensional inks into 3D building blocks. The result is the 3D/3D vdW mono- and heterostructures that are mechanically robust, electrically conductive, electrochemically active over a broad pH range and even radiation tolerant in nature.Van der Waals heterostructures stack together 2D materials to achieve unique performance. Here, 3D/3D heterostructures are created by inkjet printing of 2D MoS2 and reduced graphene oxide, and demonstrated for a heterostructure catalyst for the hydrogen evolution reaction.

Two-dimensional (2D) semiconducting monolayers such as transition metal dichalcogenides (TMDs) are promising channel materials to extend Moore's Law in advanced electronics. Synthetic TMD layers from chemical vapor deposition (CVD) are scalable for fabrication but notorious for their high defect densities. Therefore, innovative endeavors on growth reaction to enhance their quality are urgently needed. Here, we report that the hydroxide W species, an extremely pure vapor phase metal precursor form, is very efficient for sulfurization, leading to about one order of magnitude lower defect density compared to those from conventional CVD methods. The field-effect transistor (FET) devices based on the proposed growth reach a peak electron mobility ~200 cm /Vs (~800 cm /Vs) at room temperature (15 K), comparable to those from exfoliated flakes. The FET device with a channel length of 100 nm displays a high on-state current of ~400 µA/µm, encouraging the industrialization of 2D materials.

Enhancing light-matter coupling in two-dimensional (2D) semiconductors such as transition metal dichalcogenide monolayers remains a central challenge in nanophotonics due to their atomic thickness, which limits their interaction volume with light. Here, we demonstrate that first-order quasi-bound states in the continuum (quasi-BICs) supported by a freestanding metasurface provide exceptionally strong surface field enhancement, enabling efficient coupling with a tungsten disulfide (WS2) monolayer. Triangular-lattice polymer patterns on silicon nitride membranes are fabricated to realize these higher-order modes. Simulations reveal that first-order quasi-BICs exhibit much stronger field enhancement than zeroth-order modes at the top surface where the WS2 monolayer is placed. Photoluminescence (PL) measurements confirm a remarkable PL enhancement factor of 127 for first-order quasi-BICs, over six times larger than that of zeroth-order quasi-BICs. These results establish higher-order BICs in freestanding metasurfaces as a powerful route to engineer light-matter interactions in 2D semiconductors for advanced nanophotonic and quantum photonic applications.