Atomically engineering interlayer symmetry operations of two-dimensional crystals.

Crystal symmetry, which governs the local atomic coordination and bonding environment, is one of the paramount constituents that intrinsically dictate materials' functionalities. However, engineering crystal symmetry is not straightforward due to the isotropically strong covalent/ionic bonds in crystals. Layered two-dimensional materials offer an ideal platform for crystal engineering because of the ease of interlayer symmetry operations.

Surface-Assisted Passivation Growth of 2D Ultrathin β-BiO Crystals for High-Performance Polarization-Sensitive Photodetectors.

2D nonlayered materials (NLMs) have garnered considerable attention due to unique surface structure and bright application prospect. However, owing to the strong interatomic forces caused by intrinsic isotropic chemical bonds in all directions, the direct synthesis of ultrathin and large area 2D NLMs remains a tremendous challenge. Here, the surface-assisted passivation growth strategy is designed to synthesize ultrathin and large size β-BiO crystals with the thickness down to 0.

Space-Confined Vertical Growth of Large-Size Organic Semiconductor Single Crystals.

Organic semiconductor single crystals (OSSCs) have garnered considerable attention because of their high charge mobility and atomic-scale smooth surface. However, their large-size high-quality preparation remains challenging due to the inevitable defects and limited growth speed brought by traditional epitaxial growth. Here, we demonstrate a space-confined strategy, named out-of-plane microspacing in-air sublimation (OPMAS), for growing vertically millimeter-sized OSSCs in several minutes by revolutionizing the heterogeneous epitaxial growth mode severely depending on substrates into a spontaneous homogeneous growth mode free from substrates.

Enhanced carrier transport of monolayer MoSe through interlayer coupling with grown metal-organic frameworks.

Exceptional interlayer coupling of organic-inorganic vdWHs is paramount for enhancing electron mobility. Herein, we report a novel transfer-free method to fabricate MoSe/Ni(HITP) vdWHs. The MOF film promotes interfacial charge transfer, leading to a threefold increase in electron mobility.

Atomic engineering of two-dimensional materials liquid metals.

Two-dimensional (2D) materials, known for their distinctive electronic, mechanical, and thermal properties, have attracted considerable attention. The precise atomic-scale synthesis of 2D materials opens up new frontiers in nanotechnology, presenting novel opportunities for material design and property control but remains challenging due to the high expense of single-crystal solid metal catalysts. Liquid metals, with their fluidity, ductility, dynamic surface, and isotropy, have significantly enhanced the catalytic processes crucial for synthesizing 2D materials, including decomposition, diffusion, and nucleation, thus presenting an unprecedented precise control over material structures and properties.

Recent progress in emerging two-dimensional organic-inorganic van der Waals heterojunctions.

Two-dimensional (2D) materials have attracted significant attention in recent decades due to their exceptional optoelectronic properties. Among them, to meet the growing demand for multifunctional applications, 2D organic-inorganic van der Waals (vdW) heterojunctions have become increasingly popular in the development of optoelectronic devices. These heterojunctions demonstrate impressive capability to synergistically combine the favourable characteristics of organic and inorganic materials, thereby offering a wide range of advantages.

Phase and Composition Engineering of Self-Intercalated 2D Metallic Tantalum Sulfide for Second-Harmonic Generation.

Self-intercalation in two-dimensional (2D) materials is significant, as it offers a versatile approach to modify material properties, enabling the creation of interesting functional materials, which is essential in advancing applications across various fields. Here, we define ic-2D materials as covalently bonded compounds that result from the self-intercalation of a metal into layered 2D compounds. However, precisely growing ic-2D materials with controllable phases and self-intercalation concentrations to fully exploit the applications in the ic-2D family remains a great challenge.

Liquid metal catalyzed chemical vapor deposition towards morphology engineering of 2D epitaxial heterostructures.

The past decades have witnessed significant advancements in the growth of two-dimensional (2D) materials, offering a wide range of potential applications in the fields of electronics, optoelectronics, energy storage, sensors, catalysis, and biomedical treatments. Epitaxial heterostructures based on 2D materials, including vertical heterostructures, lateral structures, and superlattices, have emerged as novel material systems to manipulate the intrinsic properties and unlock new functionalities. Therefore, the development of controllable preparation methods for tailored epitaxial heterostructures serves as a fundamental basis for extensive property investigation and further application exploration.

Ultralow-Power Vertical Transistors for Multilevel Decoding Modes.

Organic field-effect transistors with parallel transmission and learning functions are of interest in the development of brain-inspired neuromorphic computing. However, the poor performance and high power consumption are the two main issues limiting their practical applications. Herein, an ultralow-power vertical transistor is demonstrated based on transition-metal carbides/nitrides (MXene) and organic single crystal.

Continuous orientated growth of scaled single-crystal 2D monolayer films.

Single-crystal 2D materials have attracted a boom of scientific and technological activities. Recently, chemical vapor deposition (CVD) shows great promise for the synthesis of high-quality 2D materials owing to high controllability, high scalability and ultra-low cost. Two types of strategies have been developed: one is single-seed method, which focuses on the ultimate control of the density of nucleation into only one nucleus and the other is a multi-seed approach, which concentrates on the precise engineering of orientation of nuclei into a uniform alignment.

Additive-Assisted Growth of Scaled and Quality 2D Materials.

2D materials are increasingly becoming key components in modern electronics because of their prominent electronic and optoelectronic properties. The central and premise to the entire discipline of 2D materials lie in the high-quality and scaled preparations. The chemical vapor deposition (CVD) method offers compelling benefits in terms of scalability and controllability in shaping large-area and high-quality 2D materials.

A minireview on chemical vapor deposition growth of wafer-scale monolayer -BN single crystals.

Hexagonal boron nitride (-BN), with its excellent stability, flat surface, and large bandgap, plays a role in a variety of fundamental science and technology fields. The past few years have witnessed significant development in the scaled growth of -BN single crystals. Currently, the size of -BN crystal can be reached up to wafer-scale, paving the way towards industrial production and commercial applications.

When graphene meets white graphene - recent advances in the construction of graphene and h-BN heterostructures.

2D heterostructures have very recently witnessed a boom in scientific and technological activities owing to the customized spatial orientation and tailored physical properties. A large amount of 2D heterostructures have been constructed on the basis of the combination of mechanical exfoliation and located transfer method, opening wide possibilities for designing novel hybrid systems with tuned structures, properties, and applications. Among the as-developed 2D heterostructures, in-plane graphene and h-BN heterostructures have drawn the most attention in the past few decades.

Controlled growth of 2D ultrathin GaO crystals on liquid metal.

2D metal oxides (2DMOs) have drawn intensive interest in the past few years owing to their rich surface chemistry and unique electronic structures. Striving for large-scale and high-quality novel 2DMOs is of great significance for developing future nano-enabled technologies. In this work, we demonstrate for the first time controllable growth of highly crystalline 2D ultrathin GaO single crystals on liquid Ga by the chemical vapor deposition approach.

Recent Advances in Growth of Large-Sized 2D Single Crystals on Cu Substrates.

Large-scale and high-quality 2D materials have been an emerging and promising choice for use in modern chemistry and physics owing to their fascinating property profile. The past few years have witnessed inspiringly progressing development in controlled fabrication of large-sized and single-crystal 2D materials. Among those production methods, chemical vapor deposition (CVD) has drawn the most attention because of its fine control over size and quality of 2D materials by modulating the growth conditions.

Graphene-Induced in Situ Growth of Monolayer and Bilayer 2D SiC Crystals Toward High-Temperature Electronics.

A reproducible graphene-induced in situ process is demonstrated for the first time for growing large-scale monolayer and bilayer cubic silicon carbide (SiC) crystals on a liquid Cu surface by chemical vapor deposition (CVD) method. Precise control over the morphology of SiC crystals is further realized by modulating growth conditions, thus leading to the formation of several shaped SiC crystals ranging from triangular, rectangular, pentagonal, and even to hexagonal kind. Simulations based on density functional theory are carried out to elucidate the growth mechanism of SiC flakes with various morphologies, which are in striking consistency with experimental observations.

High-Concentration Niobium-Substituted WS Basal Domains with Reconfigured Electronic Band Structure for Hydrogen Evolution Reaction.

Extrinsically controlling the intrinsic activity and stability of two-dimensional (2D) semiconducting materials by substitutional doping is crucial for energy-related applications. However, an in situ transition-metal doping strategy for uniform and large-area chemical vapor deposited 2D semiconductors remains a formidable challenge. Here, we successfully synthesize highly uniform niobium-substituted tungsten disulfide (Nb-WS) monolayers, with a doping concentration of nearly 7% and sizes reaching 100 μm, through a metal dopant precursor route, using salt-catalyzed chemical vapor deposition (CVD).

Primary Nucleation-Dominated Chemical Vapor Deposition Growth for Uniform Graphene Monolayers on Dielectric Substrate.

Direct chemical vapor deposition growth of high quality graphene on dielectric substrates holds great promise for practical applications in electronics and optoelectronics. However, graphene growth on dielectrics always suffers from the issues of inhomogeneity and/or poor quality. Here, we first reveal that a novel precursor-modification strategy can successfully suppress the secondary nucleation of graphene to evolve ultrauniform graphene monolayer film on dielectric substrates.

Formation of Twinned Graphene Polycrystals.

Liquid metals have been widely used as substrates to grow graphene and other 2D materials. On a homogeneous and isotropic liquid surface, a polycrystalline 2D material is formed by coalescence of many randomly nucleated single-crystal islands, and as a result, the domains in a polycrystal are expected to be randomly aligned. Here, we report the unexpected finding that only 30°-twinned graphene polycrystals are grown on a liquid Cu surface.

Thermal-Assisted Vertical Electron Injections in Few-Layer Pyramidal-Structured MoS Crystals.

The interlayer screening effects and charge conduction mechanisms in atomically thin two-dimensional (2D) materials are crucial for electronics and optoelectronics applications. However, such effects remain largely unexplored in chemical vapor deposition (CVD)-grown molybdenum disulfide (MoS) crystals. Here, we report a controllable CVD-grown monolayer MoS and layer-by-layer pyramidal-structured MoS crystals with an oxidized Mo foil precursor.

Location-selective growth of two-dimensional metallic/semiconducting transition metal dichalcogenide heterostructures.

An electrical contact between metallic electrodes and semiconductors is critical for the performance of electronic and optoelectronic devices. Two-dimensional (2D) transition metal dichalcogenides (TMDs) contain semiconducting, metallic and insulating material members, which enables the fabrication of highly integrated electronic devices fully based on 2D TMDs. However, location-selective synthesis of metallic/semiconducting heterostructures by a chemical vapor deposition (CVD) method has rarely been reported.

Edge Segregated Polymorphism in 2D Molybdenum Carbide.

Molybdenum carbide (Mo C), a class of unterminated MXene, is endowed with rich polymorph chemistry, but the growth conditions of the various polymorphs are not understood. Other than the most commonly observed T-phase Mo C, little is known about other phases. Here, Mo C crystals are successfully grown consisting of mixed polymorphs and polytypes via a diffusion-mediated mechanism, using liquid copper as the diffusion barrier between the elemental precursors of Mo and C.

Effects of precursor pre-treatment on the vapor deposition of WS monolayers.

Transition metal oxide powders have been widely used as the growth precursors for monolayer transition metal dichalcogenides (TMDCs) in chemical vapor deposition (CVD). It has been proposed that metal oxide precursors in the gas phase undergo a two-step reaction during CVD growth, where transition metal sub-oxides are likely formed first and then the sulfurization of these sub-oxides leads to the formation of TMDCs. However, the effects of stoichiometry of transition metal oxide precursors on the growth of TMDC monolayers have not been studied yet.

Recent Advances in Growth of Novel 2D Materials: Beyond Graphene and Transition Metal Dichalcogenides.

Since the discovery of graphene just over a decade ago, 2D materials have been a central focus of materials research and engineering because of their unique properties and potential of revealing intriguing new phenomena. In the past few years, transition metal dichalcogenides (TMDs) have also attracted considerable attention because of the intrinsically opened bandgap. The exceptional properties and potential applications of graphene and TMDs have inspired explosive efforts to discover novel 2D materials.