Observation of phonon Stark effect.

Stark effect, the electric-field analogue of magnetic Zeeman effect, is one of the celebrated phenomena in modern physics and appealing for emergent applications in electronics, optoelectronics, as well as quantum technologies. While in condensed matter it has prospered only for excitons, whether other collective excitations can display Stark effect remains elusive. Here, we report the observation of phonon Stark effect in a two-dimensional quantum system of bilayer 2H-MoS.

Layer-by-layer epitaxy of multi-layer MoS wafers.

The 2D semiconductor of MoS has great potential for advanced electronics technologies beyond silicon. So far, high-quality monolayer MoS wafers have been available and various demonstrations from individual transistors to integrated circuits have also been shown. In addition to the monolayer, multilayers have narrower band gaps but improved carrier mobilities and current capacities over the monolayer.

Giant anisotropic photonics in the 1D van der Waals semiconductor fibrous red phosphorus.

A confined electronic system can host a wide variety of fascinating electronic, magnetic, valleytronic and photonic phenomena due to its reduced symmetry and quantum confinement effect. For the recently emerging one-dimensional van der Waals (1D vdW) materials with electrons confined in 1D sub-units, an enormous variety of intriguing physical properties and functionalities can be expected. Here, we demonstrate the coexistence of giant linear/nonlinear optical anisotropy and high emission yield in fibrous red phosphorus (FRP), an exotic 1D vdW semiconductor with quasi-flat bands and a sizeable bandgap in the visible spectral range.

In Situ Oxygen Doping of Monolayer MoS for Novel Electronics.

In 2D semiconductors, doping offers an effective approach to modulate their optical and electronic properties. Here, an in situ doping of oxygen atoms in monolayer molybdenum disulfide (MoS ) is reported during the chemical vapor deposition process. Oxygen concentrations up to 20-25% can be reliable achieved in these doped monolayers, MoS O .

Wafer-Scale Highly Oriented Monolayer MoS with Large Domain Sizes.

Two-dimensional molybdenum disulfide (MoS) is an emergent semiconductor with great potential in next-generation scaled-up electronics, but the production of high-quality monolayer MoS wafers still remains a challenge. Here, we report an epitaxy route toward 4 in. monolayer MoS wafers with highly oriented and large domains on sapphire.

Atomic-scale observations of electrical and mechanical manipulation of topological polar flux closure.

The ability to controllably manipulate complex topological polar configurations such as polar flux-closures via external stimuli may allow the construction of new electromechanical and nanoelectronic devices. Here, using atomically resolved in situ scanning transmission electron microscopy, we find that the polar flux-closures in PbTiO/SrTiO superlattice films are mobile and can be reversibly switched to ordinary single ferroelectric or domains under an applied electric field or stress. Specifically, the electric field initially drives movement of a flux-closure via domain wall motion and then breaks it to form intermediate / striped domains, whereas mechanical stress first squeezes the core of a flux-closure toward the interface and then form / domains with disappearance of the core.

Employing defected monolayer MoS as charge storage materials.

Recently, various two-dimensional (2D) materials have been employed in charge trapping memories as the charge trapping layer instead of conventional metal/semiconductor thin films or discrete particles. Such ultra-thin charge trapping layers are beneficial to the development of miniaturized devices, which is a trend in modern semiconductor technology. 2D MoS is an alternative charge trapping material, but previous investigations have been limited to their multilayers.

Giant Valley Coherence at Room Temperature in 3R WS with Broken Inversion Symmetry.

Breaking the space-time symmetries in materials can markedly influence their electronic and optical properties. In 3R-stacked transition metal dichalcogenides, the explicitly broken inversion symmetry enables valley-contrasting Berry curvature and quantization of electronic angular momentum, providing an unprecedented platform for valleytronics. Here, we study the valley coherence of 3R WS large single-crystal with thicknesses ranging from monolayer to octalayer at room temperature.