Identifying the Non-Identical Outermost Selenium Atoms and Invariable Band Gaps across the Grain Boundary of Anisotropic Rhenium Diselenide.

Rhenium diselenide (ReSe) is a unique transition-metal dichalcogenide (TMDC) possessing distorted 1T structure with a triclinic symmetry, strong in-plane anisotropy, and promising applications in optoelectronics and energy-related fields. So far, the structural and physical properties of ReSe are mainly uncovered by transmission electron microscopy and spectroscopy characterizations. Herein, by combining scanning tunneling microscopy and spectroscopy (STM and STS) with first-principles calculations, we accomplish the on-site atomic-scale identification of the top four non-identical Se atoms in a unit cell of the anisotropic monolayer ReSe on the Au substrate.

Batch production of 6-inch uniform monolayer molybdenum disulfide catalyzed by sodium in glass.

Monolayer transition metal dichalcogenides (TMDs) have become essential two-dimensional materials for their perspectives in engineering next-generation electronics. For related applications, the controlled growth of large-area uniform monolayer TMDs is crucial, while it remains challenging. Herein, we report the direct synthesis of 6-inch uniform monolayer molybdenum disulfide on the solid soda-lime glass, through a designed face-to-face metal-precursor supply route in a facile chemical vapor deposition process.

Vertical 1T-TaS Synthesis on Nanoporous Gold for High-Performance Electrocatalytic Applications.

2D metallic TaS is acting as an ideal platform for exploring fundamental physical issues (superconductivity, charge-density wave, etc.) and for engineering novel applications in energy-related fields. The batch synthesis of high-quality TaS nanosheets with a specific phase is crucial for such issues.

Temperature-dependent Raman spectroscopy studies of the interface coupling effect of monolayer ReSe single crystals on Au foils.

Rhenium diselenide (ReSe), which bears in-plane anisotropic optical and electrical properties, is of considerable interest for its excellent applications in novel devices, such as polarization-sensitive photodetectors and integrated polarization-controllers. However, great challenges to date in the controllable synthesis of high-quality ReSe have hindered its in-depth investigations and practical applications. Herein, we report a feasible synthesis of monolayer single-crystal ReSe flakes on the Au foil substrate by using a chemical vapor deposition route.

Two-dimensional metallic tantalum disulfide as a hydrogen evolution catalyst.

Two-dimensional metallic transition metal dichalcogenides are emerging as prototypes for uncovering fundamental physical phenomena, such as superconductivity and charge-density waves, as well as for engineering-related applications. However, the batch production of such envisioned transition metal dichalcogenides remains challenging, which has hindered the aforementioned explorations. Herein, we fabricate thickness-tunable tantalum disulfide flakes and centimetre-sized ultrathin films on an electrode material of gold foil via a facile chemical vapour deposition route.

Tuning Excitonic Properties of Monolayer MoS with Microsphere Cavity by High-Throughput Chemical Vapor Deposition Method.

Tuning the optical properties of 2D direct bandgap semiconductors is crucial for applications in photonic light source, optical communication, and sensing. In this work, the excitonic properties of molybdenum disulphide (MoS ) are successfully tuned by directly depositing it onto silica microsphere resonators using chemical vapor deposition method. Multiple whispering gallery mode (WGM) peaks in the emission wavelength range of ≈650-750 nm are observed under continuous wave excitation at room temperature.

Van der Waals Epitaxial Growth of 2D Metallic Vanadium Diselenide Single Crystals and their Extra-High Electrical Conductivity.

2D metallic transition-metal dichalcogenides (MTMDs) have recently emerged as a new class of materials for the engineering of novel electronic phases, 2D superconductors, magnets, as well as novel electronic applications. However, the mechanical exfoliation route is predominantly used to obtain such metallic 2D flakes, but the batch production remains challenging. Herein, the van der Waals epitaxial growth of monocrystalline, 1T-phase, few-layer metallic VSe nanosheets on an atomically flat mica substrate via a "one-step" chemical vapor deposition method is reported.

Temperature-Triggered Sulfur Vacancy Evolution in Monolayer MoS /Graphene Heterostructures.

The existence of defects in 2D semiconductors has been predicted to generate unique physical properties and markedly influence their electronic and optoelectronic properties. In this work, it is found that the monolayer MoS prepared by chemical vapor deposition is nearly defect-free after annealing under ultrahigh vacuum conditions at ≈400 K, as evidenced by scanning tunneling microscopy observations. However, after thermal annealing process at ≈900 K, the existence of dominant single sulfur vacancies and relatively rare vacancy chains (2S, 3S, and 4S) is convinced in monolayer MoS as-grown on Au foils.

Irreparable Defects Produced by the Patching of h-BN Frontiers on Strongly Interacting Re(0001) and Their Electronic Properties.

Clarifying the origin and the electronic properties of defects in materials is crucial since the mechanical, electronic and magnetic properties can be tuned by defects. Herein, we find that, for the growth of h-BN monolayer on Re(0001), the patching frontiers of different domains can be classified into three types, i.e.

Direct Chemical Vapor Deposition Growth and Band-Gap Characterization of MoS/h-BN van der Waals Heterostructures on Au Foils.

Stacked transition-metal dichalcogenides on hexagonal boron nitride (h-BN) are platforms for high-performance electronic devices. However, such vertical stacks are usually constructed by the layer-by-layer polymer-assisted transfer of mechanically exfoliated layers. This inevitably causes interfacial contamination and device performance degradation.

Strong Adlayer-Substrate Interactions "Break" the Patching Growth of h-BN onto Graphene on Re(0001).

Hetero-epitaxial growth of hexagonal boron nitride (h-BN) from the edges of graphene domains or vice versa has been widely observed during synthesis of in-plane heterostructures of h-BN-G on Rh(111), Ir(111), and even Cu foil. We report that on a strongly coupled Re(0001) substrate via a similar two-step sequential growth strategy, h-BN preferably nucleated on the edges of Re(0001) steps rather than on the edges of existing graphene domains. Statistically, one-third of the domain boundaries of graphene and h-BN were patched seamlessly, and the others were characterized by obvious "defect lines" when the total coverage approached a full monolayer.

Temperature-Mediated Selective Growth of MoS /WS and WS /MoS Vertical Stacks on Au Foils for Direct Photocatalytic Applications.

A growth-temperature-mediated two-step chemical vapor deposition strategy is designed to synthesize MoS /WS and WS /MoS stacks on Au foils. Predominantly A-A stacked MoS /WS and A-B stacked WS /MoS are selectively achieved and confirmed. Relative enhancements or reductions in photocatalytic activities of MoS /WS or WS /MoS are observed under illumination, because the type-II band alignment enables directional electron flow from electrode to active site.

Modulating the Electronic Properties of Monolayer Graphene Using a Periodic Quasi-One-Dimensional Potential Generated by Hex-Reconstructed Au(001).

The structural and electronic properties of monolayer graphene synthesized on a periodically reconstructed substrate can be widely modulated by the generation of superstructure patterns, thereby producing interesting physical properties, such as magnetism and superconductivity. Herein, using a facile chemical vapor deposition method, we successfully synthesized high-quality monolayer graphene with a uniform thickness on Au foils. The hex-reconstruction of Au(001), which is characterized by striped patterns with a periodicity of 1.

Periodic Modulation of the Doping Level in Striped MoS₂ Superstructures.

Although the recently discovered monolayer transition metal dichalcogenides exhibit novel electronic and optical properties, fundamental physical issues such as the quasiparticle bandgap tunability and the substrate effects remain undefined. Herein, we present the report of a quasi-one-dimensional periodically striped superstructure for monolayer MoS2 on Au(100). The formation of the unique striped superstructure is found to be mainly modulated by the symmetry difference between MoS2 and Au(100) and their lattice mismatch.

All Chemical Vapor Deposition Synthesis and Intrinsic Bandgap Observation of MoS2 /Graphene Heterostructures.

A facile all-chemical vapor deposition approach is designed, which allows both sequentially grown Gr and monolayer MoS2 in the same growth process, thus allowing the direct construction of MoS2 /Gr vertical heterostructures on Au foils. A weak n-doping effect and an intrinsic bandgap of MoS2 are obtained from MoS2 /Gr/Au via scanning tunneling microscopy and spectroscopy characterization. The exciton binding energy is accurately deduced by combining photoluminescence measurements.

Grain Boundary Structures and Electronic Properties of Hexagonal Boron Nitride on Cu(111).

Grain boundaries (GBs) of hexagonal boron nitride (h-BN) grown on Cu(111) were investigated by scanning tunneling microscopy/spectroscopy (STM/STS). The first experimental evidence of the GBs composed of square-octagon pairs (4|8 GBs) was given, together with those containing pentagon-heptagon pairs (5|7 GBs). Two types of GBs were found to exhibit significantly different electronic properties, where the band gap of the 5|7 GB was dramatically decreased as compared with that of the 4|8 GB, consistent with our obtained result from density functional theory (DFT) calculations.