Achieving near-perfect light absorption in atomically thin transition metal dichalcogenides through band nesting.

Near-perfect light absorbers (NPLAs), with absorbance, [Formula: see text], of at least 99%, have a wide range of applications ranging from energy and sensing devices to stealth technologies and secure communications. Previous work on NPLAs has mainly relied upon plasmonic structures or patterned metasurfaces, which require complex nanolithography, limiting their practical applications, particularly for large-area platforms. Here, we use the exceptional band nesting effect in TMDs, combined with a Salisbury screen geometry, to demonstrate NPLAs using only two or three uniform atomic layers of transition metal dichalcogenides (TMDs).

Vertical Conductivity and Topography in Electrostrictive Germanium Sulfide Microribbon via Conductive Atomic Force Microscopy.

Layered group IV monochalcogenides are two-dimensional (2D) semiconducting materials with unique crystal structures and novel physical properties. Here, we report the growth of single crystalline GeS microribbons using the chemical vapor transport process. By using conductive atomic force microscopy, we demonstrated that the conductive behavior in the vertical direction was mainly affected by the Schottky barriers between GeS and both electrodes.

Stabilization of Chemical-Vapor-Deposition-Grown WS Monolayers at Elevated Temperature with Hexagonal Boron Nitride Encapsulation.

Chemical vapor deposition (CVD)-grown flakes of high-quality monolayers of WS can be stabilized at elevated temperatures by encapsulation with several layer hexagonal boron nitride (BN), but to different degrees in the presence of ambient air, flowing N, and flowing forming gas (95% N, 5% H). The best passivation of WS at elevated temperature occurs for -BN-covered samples with flowing N (after heating to 873 K), as judged by optical microscopy and photoluminescence (PL) intensity after a heating/cooling cycle. Stability is worse for uncovered samples, but best with flowing forming gas.

Multioperation-Mode Light-Emitting Field-Effect Transistors Based on van der Waals Heterostructure.

2D semiconductors have shown great potential for application to electrically tunable optoelectronics. Despite the strong excitonic photoluminescence (PL) of monolayer transition metal dichalcogenides (TMDs), their efficient electroluminescence (EL) has not been achieved due to the low efficiency of charge injection and electron-hole recombination. Here, multioperation-mode light-emitting field-effect transistors (LEFETs) consisting of a monolayer WSe channel and graphene contacts coupled with two top gates for selective and balanced injection of charge carriers are demonstrated.

Plasma-Doped Si Nanosheets for Transistor and Junction Application.

Since the discovery of graphene, layered transition metal dichalcogenides (TMDs) have been considered promising materials for applications in various fields because of their fascinating structural features and physical properties. Doping in semiconducting TMDs is essential for their practical application. In this regard, two-dimensional (2D) Si materials have emerged as a key component of 2D electronic, optics, sensing, and spintronic devices because of their complementary metal-oxide-semiconductor (CMOS) compatibility, high-quality oxide formation, moderated bandgap, and well-established doping techniques.

Ultrafast Graphene Light Emitters.

Ultrafast electrically driven nanoscale light sources are critical components in nanophotonics. Compound semiconductor-based light sources for the nanophotonic platforms have been extensively investigated over the past decades. However, monolithic ultrafast light sources with a small footprint remain a challenge.

Low-Temperature Ohmic Contact to Monolayer MoS by van der Waals Bonded Co/h-BN Electrodes.

Monolayer MoS, among many other transition metal dichalcogenides, holds great promise for future applications in nanoelectronics and optoelectronics due to its ultrathin nature, flexibility, sizable band gap, and unique spin-valley coupled physics. However, careful study of these properties at low temperature has been hindered by an inability to achieve low-temperature Ohmic contacts to monolayer MoS, particularly at low carrier densities. In this work, we report a new contact scheme that utilizes cobalt (Co) with a monolayer of hexagonal boron nitride (h-BN) that has the following two functions: modifies the work function of Co and acts as a tunneling barrier.

Extension of the T-bridge method for measuring the thermal conductivity of two-dimensional materials.

In this paper, the T-bridge method is extended to measure the thermal properties of two-dimensional nanomaterials. We present an analysis of the measureable positions, width, and thermal resistance of two-dimensional materials. For verification purposes, the thermal conductivity of a SiO nanoribbon was measured.

Growth of Silicon Nanosheets Under Diffusion-Limited Aggregation Environments.

The two-dimensional (2D) growth of cubic-structured (silicon) Si nanosheets (SiNSs) was investigated. Freestanding, single-crystalline SiNSs with a thickness of 5-20 nm were grown on various Si substrates under an atmospheric chemical vapor deposition process. Systematic investigation indicated that a diffusion-limited aggregation (DLA) environment that leads to dendritic growth in <110> directions at the initial stage is essential for 2D growth.

Magnetic In x Ga 1 - x N nanowires at room temperature using Cu dopant and annealing.

Single-crystal, Cu-doped In x Ga1 - x N nanowires were grown on GaN/Al2O3 substrates via a vapor-liquid-solid (VLS) mechanism using Ni/Au bi-catalysts. The typical diameter of the Cu:In x Ga1 - x N nanowires was 80 to 150 nm, with a typical length of hundreds of micrometers. The as-grown nanowires exhibited diamagnetism.

Structural modulation of silicon nanowires by combining a high gas flow rate with metal catalysts.

Unlabelled: We grew silicon nanowires (SiNWs) by a vapor-liquid-solid (VLS) mechanism using metal catalysts of gold (Au), titanium (Ti), manganese (Mn), and iron (Fe) under a high flow rate of hydrogen (H2). This combination of catalyst types and high gas flow rate revealed the potential for growing various SiNWs, including kinked SiNWs (with Au), ultra-thin SiNWs having diameters about 5 nm (with Ti), rough-surfaced SiNWs (with Mn), and ribbon-shaped SiNWs tens of microns in width (with Fe). The high flow rate of gas affects the VLS mechanism differently for each combination; for example, it induces an unstable solid-liquid interfaces (with Au), active etching of the catalyst (with Ti), sidewall deposition by a vapor-solid (VS) mechanism, and an asymmetric precipitation of Si in the catalyst (with Fe).