Anti-wrinkle properties of Angelica gigas Nakai root extracts using mineral-rich water.

Background: Angelica gigas Nakai is used as an herbal pharmaceutical material in Korea.

Aims: To investigate the anti-wrinkle effects of A. gigas Nakai root extracts (ARE) using mineral-rich water in in vitro and clinical trials.

Edge Contact for Carrier Injection and Transport in MoS Field-Effect Transistors.

The contact properties of van der Waals layered semiconducting materials are not adequately understood, particularly for edge contact. Edge contact is extremely helpful in the case of graphene, for producing efficient contacts to vertical heterostructures, and for improving the contact resistance through strong covalent bonding. Herein, we report on edge contacts to MoS of various thicknesses.

Anomalous Conductance near Percolative Metal-Insulator Transition in Monolayer MoS at Low Voltage Regime.

Conductivity of the insulating phase increases generally at an elevated drain-source voltage due to the field-enhanced hopping or heating effect. Meanwhile, a transport mechanism governed by percolation in a low compensated semiconductor gives rise to the reduced conductivity at a low-field regime. Here, in addition to this behavior, we report the anomalous conductivity behavior to transform from a percolative metallic to an insulating phase at the low voltage regime in monolayer molybdenum disulfide (MoS).

Soft Coulomb gap and asymmetric scaling towards metal-insulator quantum criticality in multilayer MoS.

Quantum localization-delocalization of carriers are well described by either carrier-carrier interaction or disorder. When both effects come into play, however, a comprehensive understanding is not well established mainly due to complexity and sparse experimental data. Recently developed two-dimensional layered materials are ideal in describing such mesoscopic critical phenomena as they have both strong interactions and disorder.

Unsaturated Drift Velocity of Monolayer Graphene.

We observe that carriers in graphene can be accelerated to the Fermi velocity without heating the lattice. At large Fermi energy | E| > 110 meV, electrons excited by a high-power terahertz pulse E relax by emitting optical phonons, resulting in heating of the graphene lattice and optical-phonon generation. This is owing to enhanced electron-phonon scattering at large Fermi energy, at which the large phase space is available for hot electrons.

Tunable Mobility in Double-Gated MoTe Field-Effect Transistor: Effect of Coulomb Screening and Trap Sites.

There is a general consensus that the carrier mobility in a field-effect transistor (FET) made of semiconducting transition-metal dichalcogenides (s-TMDs) is severely degraded by the trapping/detrapping and Coulomb scattering of carriers by ionic charges in the gate oxides. Using a double-gated (DG) MoTe FET, we modulated and enhanced the carrier mobility by adjusting the top- and bottom-gate biases. The relevant mechanism for mobility tuning in this device was explored using static DC and low-frequency (LF) noise characterizations.

Junction-Structure-Dependent Schottky Barrier Inhomogeneity and Device Ideality of Monolayer MoS Field-Effect Transistors.

Although monolayer transition metal dichalcogenides (TMDs) exhibit superior optical and electrical characteristics, their use in digital switching devices is limited by incomplete understanding of the metal contact. Comparative studies of Au top and edge contacts with monolayer MoS reveal a temperature-dependent ideality factor and Schottky barrier height (SBH). The latter originates from inhomogeneities in MoS caused by defects, charge puddles, and grain boundaries, which cause local variation in the work function at Au-MoS junctions and thus different activation temperatures for thermionic emission.

Photocurrent Switching of Monolayer MoS Using a Metal-Insulator Transition.

We achieve switching on/off the photocurrent of monolayer molybdenum disulfide (MoS) by controlling the metal-insulator transition (MIT). N-type semiconducting MoS under a large negative gate bias generates a photocurrent attributed to the increase of excess carriers in the conduction band by optical excitation. However, under a large positive gate bias, a phase shift from semiconducting to metallic MoS is caused, and the photocurrent by excess carriers in the conduction band induced by the laser disappears due to enhanced electron-electron scattering.

Electrical Transport Properties of Polymorphic MoS2.

The engineering of polymorphs in two-dimensional layered materials has recently attracted significant interest. Although the semiconducting (2H) and metallic (1T) phases are known to be stable in thin-film MoTe2, semiconducting 2H-MoS2 is locally converted into metallic 1T-MoS2 through chemical lithiation. In this paper, we describe the observation of the 2H, 1T, and 1T' phases coexisting in Li-treated MoS2, which result in unusual transport phenomena.