Tabletop Fabrication of High-Performance MoS Field-Effect Transistors.

A simple way to prepare field-effect transistors (FETs) using MoS on tabletop is presented. Conductive silver paste was applied onto chemical vapor deposition (CVD)-grown MoS as Ohmic-contact electrodes. Heating the device in vacuum further enhances the performance without damage.

Anisotropic Electrical Conductivity of a Single-Crystalline Oxo-Bridged CrMo Heterometallic Complex.

A new oxo-bridged chromium-molybdenum heterometallic complex, O-CrMoHC ([Cr(MoO)O(OAc)(DMF)]·2DMF), was synthesized by using a simple solvothermal reaction. In this complex, the octahedrally coordinated Cr(III) and tetrahedrally coordinated Mo(VI) metal centers are bridged by oxo ligands. O-CrMoHC has in-plane π-conjugation systems, which are interconnected by noncoordinating DMF molecules.

Growth of Monolayer and Multilayer MoS Films by Selection of Growth Mode: Two Pathways via Chemisorption and Physisorption of an Inorganic Molecular Precursor.

We report facile growth methods for high-quality monolayer and multilayer MoS films using MoOCl as the vapor-phase molecular Mo precursor. Compared to the conventional covalent solid-type Mo precursors, the growth pressure of MoOCl can be precisely controlled. This enables the selection of growth mode by adjusting growth pressure, which facilitates the control of the growth behavior as the growth termination at a monolayer or as the continuous growth to a multilayer.

Growth and Interlayer Engineering of 2D Layered Semiconductors for Future Electronics.

Layered materials that do not form a covalent bond in a vertical direction can be prepared in a few atoms to one atom thickness without dangling bonds. This distinctive characteristic of limiting thickness around the sub-nanometer level allowed scientists to explore various physical phenomena in the quantum realm. In addition to the contribution to fundamental science, various applications were proposed.

Fast and Facile Biodegradation of Polystyrene by the Gut Microbial Flora of Larvae.

Polystyrene (PS), which accounts for a significant fraction of plastic wastes, is difficult to biodegrade due to its unique molecular structure. Therefore, biodegradation and chemical modification of PS are limited. In this study, we report PS biodegradation by the larvae of the darkling beetle (Coleoptera: Tenebrionidae).

Facile and rapid synthesis of crystalline quadruply bonded Cr(ii) acetate coordinated with axial ligands.

A quadruple bond formed between d-block or f-block atoms is an interesting research topic due to its unique nature including a supershort bonding distance and narrow energy gap between δ and δ*. Among various multiply bonded complexes, quadruply bonded Cr(ii) acetates are considered useful to control the δ-δ* energy gap by the Lewis basicity of additional ligands. However, the synthesis and preparation of the high-quality, large-sized crystals of Cr(ii) acetates coordinated with axial ligands (Cr(OAc)L) have been difficult due to their vulnerability to O, a representative oxidizing agent under aerobic conditions.

Revealing the Role of Gold in the Growth of Two-Dimensional Molybdenum Disulfide by Surface Alloy Formation.

The formation of Mo/Au surface alloy during Au-assisted chemical vapor deposition (CVD) of MoS is confirmed by a series of control experiments. A metal-organic chemical vapor deposition (MOCVD) system is adapted to conduct two-dimensional MoS growth in a controlled environment. Sequential injection of Mo and S precursors, which does not yield any MoS on SiO /Si, grows atomically thin MoS on Au, indicating the formation of an alloy phase.

Transfer-Free, Large-Scale Growth of High-Quality Graphene on Insulating Substrate by Physical Contact of Copper Foil.

High-quality, large-area, single-layer graphene was directly grown on top of a quartz substrate by a low-pressure chemical vapor deposition (CVD) process using Cu vapor as a catalyst. In this process, continuous generation and supply of highly concentrated Cu vapor is the key to the growth of large-scale, high-quality graphene. It was achieved by direct physical contact, or "touch-down," of a Cu foil with an underlying sacrificial SiO /Si substrate, and the target quartz substrate was placed on top of the Cu foil, eventually having a quartz/Cu/SiO /Si sandwich structure.

Highly reproducible alkali metal doping system for organic crystals through enhanced diffusion of alkali metal by secondary thermal activation.

In this paper, we report an efficient alkali metal doping system for organic single crystals. Our system employs an enhanced diffusion method for the introduction of alkali metal into organic single crystals by controlling the sample temperature to induce secondary thermal activation. Using this system, we achieved intercalation of potassium into picene single crystals with closed packed crystal structures.

Broken-Symmetry Quantum Hall States in Twisted Bilayer Graphene.

Twisted bilayer graphene offers a unique bilayer two-dimensional-electron system where the layer separation is only in sub-nanometer scale. Unlike Bernal-stacked bilayer, the layer degree of freedom is disentangled from spin and valley, providing eight-fold degeneracy in the low energy states. We have investigated broken-symmetry quantum Hall (QH) states and their transitions due to the interplay of the relative strength of valley, spin and layer polarizations in twisted bilayer graphene.

Unique Crystallization of Fullerenes: Fullerene Flowers.

Solution-phase crystallization of fullerene molecules strongly depends on the types of solvent and their ratios because solvent molecules are easily included in the crystal lattice and distort its structure. The C70 (solute)-mesitylene (solvent) system yields crystals with various morphologies and structures, such as cubes, tubes, and imperfect rods. Herein, using C60 and C70 dissolved in mesitylene, we present a novel way to grow unique flower-shaped crystals with six symmetric petals.

Patternable large-scale molybdenium disulfide atomic layers grown by gold-assisted chemical vapor deposition.

A novel way to grow MoS2 on a large scale with uniformity and in desired patterns is developed. We use Au film as a catalyst on which [Mo(CO)6 ] vapor decomposes to form a Mo-Au surface alloy that is an ideal Mo reservoir for the growth of atomic layers of MoS2 . Upon exposure to H2 S, this surface alloy transforms into a few layers of MoS2 , which can be isolated and transferred on an arbitrary substrate.

Copper-vapor-assisted chemical vapor deposition for high-quality and metal-free single-layer graphene on amorphous SiO2 substrate.

We report that high-quality single-layer graphene (SLG) has been successfully synthesized directly on various dielectric substrates including amorphous SiO2/Si by a Cu-vapor-assisted chemical vapor deposition (CVD) process. The Cu vapors produced by the sublimation of Cu foil that is suspended above target substrates without physical contact catalyze the pyrolysis of methane gas and assist nucleation of graphene on the substrates. Raman spectra and mapping images reveal that the graphene formed on a SiO2/Si substrate is almost defect-free and homogeneous single layer.