NitingZ

We systematically studied the electronic structures of two-dimensional (2D) multilayered nickel bis(dithiolene) sheets using first-principles calculations. The monolayer is semiconducting, while all multilayers become good metals. We reveal that the metallicity mainly arises from covalent-like interlayer interaction between the 3 p z orbitals of S atoms in adjacent layers. We show that such interlayer orbital hybridization widely exists in many 2D layered materials involving extensively out-of-plane orbitals. This interlayer orbital hybridization greatly enriches the physical properties of this class of 2D layered materials compared to pure van der Waals 2D layered materials . More importantly, we demonstrate that these properties are easily tunable by controlling the interlayer distance or stacking, making them very promising in meeting the desired requirements in practical applications.

We report helium diffraction from natural MoS 2 single crystal. The high quality of the samples studied lead to the appearance of sharp and intense in-plane and out-of-plane diffraction peaks, with unusually low background. The pronounced out-of-plane features observed confirm the high corrugation of the 2D surface unit cell. The observation of diffraction features along the two main high symmetry directions allows determining the in-plane surface lattice constant with high accuracy. The measured lattice constant along ##IMG## [http://ej.iop.org/images/2053-1583/5/3/035015/tdmaabe4aieqn002.gif] and ##IMG## [http://ej.iop.org/images/2053-1583/5/3/035015/tdmaabe4aieqn003.gif] is ##IMG## [http://ej.iop.org/images/2053-1583/5/3/035015/tdmaabe4aieqn004.gif] Å. Within experimental error, the MoS 2 lattice parameter was found to remain constant in the temperature range between 90 and 522 K, i...

The remarkably strong Coulomb interaction in atomically thin transition metal dichalcogenides (TMDs) results in an extraordinarily rich many-particle physics including the formation of tightly bound excitons. Besides optically accessible bright excitonic states, these materials also exhibit a variety of dark excitons. Since they can even lie below the bright states, they have a strong influence on the exciton dynamics, lifetimes, and photoluminescence. While very recently, the presence of dark excitonic states has been experimentally demonstrated, the origin of these states, their formation, and dynamics have not been revealed yet. Here, we present a microscopic study shedding light on time- and energy-resolved formation and thermalization of bright and dark intra- and intervalley excitons as well as their impact on the photoluminescence in different TMD materials. We demonstrate that intervalley dark excitons, so far widely overlooked in current literature, play a crucial role ...

Monolayers of transition metal dichalcogenides (TMDC) mechanically exfoliated from bulk crystals have exceptional mechanical and optical properties. They are extremely flexible, sustaining mechanical strain of about 10% without breaking. Their optical properties dramatically change with applied strain. However, the fabrication of a large number of mechanical devices is tedious due to the micromechanical exfoliation process. Alternatively, monolayers can be grown by chemical vapor deposition (CVD) on the wafer scale, with the drawback of cracks and grain boundaries in the material. Therefore, it is important to investigate the mechanical properties of CVD-grown material and its potential as a material for mass production of nanomechanical devices. Here, we measure the optical absorption of CVD-grown MoS 2 monolayers with applied uniaxial tensile strain. We derive a strain-dependent shift for the A exciton of  −42 meV/%. This value is identical to MoS 2 monolay...

We theoretically study a single-electron spin-valley qubit in an electrostatically defined quantum dot in a transition metal dichalcogenide monolayer, focusing on the example of MoS 2 . Coupling of the qubit basis states for coherent control is challenging, as it requires a simultaneous flip of spin and valley. Here, we show that a tilted magnetic field together with a short-range impurity, such as a vacancy, a substitutional defect, or an adatom, can give rise to a coupling between the qubit basis states. This mechanism renders the in-plane g -factor nonzero, and allows to control the qubit with an in-plane ac electric field, akin to electrically driven spin resonance. We evaluate the dependence of the in-plane g -factor and the electrically induced qubit Rabi frequency on the type and position of the impurity. We reveal highly unconventional features of the coupling mechanism, arising from symmetry-forbidden intervalley scattering, in the case when the imp...

Tin disulfide (SnS 2 ) is a n-type semiconductor with a hexagonally layered crystal structure and has promising applications in nanoelectronics, optoelectronics and sensors. Such applications require the deposition of SnS 2 with controlled crystallinity and thickness control at monolayer level on large area substrate. Here, we investigate the nucleation and growth mechanism of two-dimensional (2D) SnS 2 by chemical vapor deposition (CVD) using SnCl 4 and H 2 S as precursors. We find that the growth mechanism of 2D SnS 2 is different from the classical layer-by-layer growth mode, by which monolayer-thin 2D transition metal dichalcogenides can be formed. In the initial nucleation stage, isolated 2D SnS 2 domains of several monolayers high are formed. Next, 2D SnS 2 crystals grow laterally while keeping a nearly constant height until layer closure is achieved, due to the higher reactivity of SnS 2