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At least 19 records

Materials Data on Rb(MoSe)3 by Materials Project

Rb(MoSe)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Rb is bonded in a 9-coordinate geometry to nine equivalent Se atoms. There are three shorter (3.61 Å) and six longer (3.65 Å) Rb–Se bond lengths. Mo is bonded in a distorted see-saw-like geometry to four equivalent Se atoms. There are a spread of Mo–Se bond distances ranging from 2.64–2.72 Å. Se is bonded in a 7-coordinate geometry to three equivalent Rb and four equivalent Mo atoms.

36 MATERIALS SCIENCE↗

Materials Data on Na(MoSe)3 by Materials Project

Na(MoSe)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Na is bonded in a 9-coordinate geometry to nine equivalent Se atoms. There are three shorter (3.26 Å) and six longer (3.44 Å) Na–Se bond lengths. Mo is bonded in a distorted see-saw-like geometry to four equivalent Se atoms. There are a spread of Mo–Se bond distances ranging from 2.64–2.72 Å. Se is bonded in a 7-coordinate geometry to three equivalent Na and four equivalent Mo atoms.

36 MATERIALS SCIENCE↗

Materials Data on Li(MoSe)3 by Materials Project

Li(MoSe)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Li is bonded in a trigonal planar geometry to three equivalent Se atoms. All Li–Se bond lengths are 2.58 Å. Mo is bonded in a distorted see-saw-like geometry to six equivalent Mo and four equivalent Se atoms. There are two shorter (2.67 Å) and four longer (2.74 Å) Mo–Mo bond lengths. There are a spread of Mo–Se bond distances ranging from 2.63–2.72 Å. Se is bonded in a 1-coordinate geometry to one Li and four equivalent Mo atoms.

36 MATERIALS SCIENCE↗

Materials Data on K(MoSe)3 by Materials Project

K(MoSe)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. K is bonded in a 9-coordinate geometry to nine equivalent Se atoms. There are three shorter (3.50 Å) and six longer (3.53 Å) K–Se bond lengths. Mo is bonded in a distorted see-saw-like geometry to four equivalent Se atoms. There are two shorter (2.65 Å) and two longer (2.73 Å) Mo–Se bond lengths. Se is bonded to three equivalent K and four equivalent Mo atoms to form a mixture of distorted edge, face, and corner-sharing SeK3Mo4 hexagonal pyramids.

36 MATERIALS SCIENCE↗

Materials Data on Tl(MoSe)3 by Materials Project

Tl(MoSe)3 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. Mo is bonded in a distorted see-saw-like geometry to six equivalent Mo and four equivalent Se atoms. There are two shorter (2.67 Å) and four longer (2.73 Å) Mo–Mo bond lengths. There are a spread of Mo–Se bond distances ranging from 2.63–2.71 Å. Tl is bonded in a trigonal planar geometry to three equivalent Se atoms. All Tl–Se bond lengths are 3.15 Å. Se is bonded in a 5-coordinate geometry to four equivalent Mo and one Tl atom.

36 MATERIALS SCIENCE↗

Materials Data on Cs(MoSe)3 by Materials Project

Cs(MoSe)3 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Cs is bonded in a 9-coordinate geometry to nine Se atoms. There are a spread of Cs–Se bond distances ranging from 3.81–3.92 Å. There are three inequivalent Mo sites. In the first Mo site, Mo is bonded in a distorted see-saw-like geometry to four Se atoms. There are a spread of Mo–Se bond distances ranging from 2.63–2.72 Å. In the second Mo site, Mo is bonded in a distorted see-saw-like geometry to four Se atoms. There are a spread of Mo–Se bond distances ranging from 2.63–2.72 Å. In the third Mo site, Mo is bonded in a distorted see-saw-like geometry to four Se atoms. There are a spread of Mo–Se bond distances ranging from 2.63–2.72 Å. There are three inequivalent Se sites. In the first Se site, Se is bonded in a 7-coordinate geometry to three equivalent Cs and four Mo atoms. In the second Se site, Se is bonded in a 7-coordinate geometry to three equivalent Cs and four Mo atoms. In the third Se site, Se is bonded in a 7-coordinate geometry to three equivalent Cs and four Mo atoms.

36 MATERIALS SCIENCE↗

Materials Data on In(MoSe)3 by Materials Project

In(MoSe)3 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are three inequivalent Mo sites. In the first Mo site, Mo is bonded in a distorted see-saw-like geometry to six Mo and four Se atoms. There are two shorter (2.68 Å) and four longer (2.74 Å) Mo–Mo bond lengths. There are a spread of Mo–Se bond distances ranging from 2.64–2.71 Å. In the second Mo site, Mo is bonded in a distorted see-saw-like geometry to six Mo and four Se atoms. There are one shorter (2.68 Å) and two longer (2.74 Å) Mo–Mo bond lengths. There are a spread of Mo–Se bond distances ranging from 2.64–2.71 Å. In the third Mo site, Mo is bonded in a distorted see-saw-like geometry to six Mo and four Se atoms. There are a spread of Mo–Se bond distances ranging from 2.64–2.71 Å. In is bonded in a trigonal planar geometry to three Se atoms. All In–Se bond lengths are 3.09 Å. There are two inequivalent Se sites. In the first Se site, Se is bonded in a 5-coordinate geometry to four Mo and one In atom. In the second Se site, Se is bonded in a 5-coordinate geometry to four Mo and one In atom.

36 MATERIALS SCIENCE↗

Materials Data on Na(MoSe)3 by Materials Project

Na(MoSe)3 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Na is bonded in a 12-coordinate geometry to three Mo and nine Se atoms. All Na–Mo bond lengths are 3.66 Å. There are a spread of Na–Se bond distances ranging from 3.28–3.50 Å. There are three inequivalent Mo sites. In the first Mo site, Mo is bonded in a distorted see-saw-like geometry to one Na and four Se atoms. There are two shorter (2.64 Å) and two longer (2.72 Å) Mo–Se bond lengths. In the second Mo site, Mo is bonded in a distorted see-saw-like geometry to one Na and four Se atoms. There are two shorter (2.64 Å) and two longer (2.72 Å) Mo–Se bond lengths. In the third Mo site, Mo is bonded in a distorted see-saw-like geometry to one Na and four Se atoms. There are two shorter (2.64 Å) and two longer (2.72 Å) Mo–Se bond lengths. There are three inequivalent Se sites. In the first Se site, Se is bonded in a 7-coordinate geometry to three equivalent Na and four Mo atoms. In the second Se site, Se is bonded in a 7-coordinate geometry to three equivalent Na and four Mo atoms. In the third Se site, Se is bonded in a 7-coordinate geometry to three equivalent Na and four Mo atoms.

36 MATERIALS SCIENCE↗

Materials Data on Ba(MoSe)3 by Materials Project

Ba(MoSe)3 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Ba is bonded in a 9-coordinate geometry to nine Se atoms. There are a spread of Ba–Se bond distances ranging from 3.43–3.49 Å. There are three inequivalent Mo sites. In the first Mo site, Mo is bonded in a distorted see-saw-like geometry to four Se atoms. There are a spread of Mo–Se bond distances ranging from 2.68–2.75 Å. In the second Mo site, Mo is bonded in a distorted see-saw-like geometry to four Se atoms. There are a spread of Mo–Se bond distances ranging from 2.68–2.75 Å. In the third Mo site, Mo is bonded in a distorted see-saw-like geometry to four Se atoms. There are two shorter (2.68 Å) and two longer (2.74 Å) Mo–Se bond lengths. There are three inequivalent Se sites. In the first Se site, Se is bonded to three equivalent Ba and four Mo atoms to form a mixture of distorted corner, edge, and face-sharing SeBa3Mo4 hexagonal pyramids. In the second Se site, Se is bonded to three equivalent Ba and four Mo atoms to form a mixture of distorted corner, edge, and face-sharing SeBa3Mo4 hexagonal pyramids. In the third Se site, Se is bonded to three equivalent Ba and four Mo atoms to form a mixture of distorted corner, edge, and face-sharing SeBa3Mo4 hexagonal pyramids.

36 MATERIALS SCIENCE↗

Materials Data on In(MoSe)3 by Materials Project

In(MoSe)3 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are three inequivalent Mo sites. In the first Mo site, Mo is bonded in a distorted see-saw-like geometry to six Mo and four Se atoms. There are two shorter (2.67 Å) and four longer (2.73 Å) Mo–Mo bond lengths. There are a spread of Mo–Se bond distances ranging from 2.64–2.72 Å. In the second Mo site, Mo is bonded in a distorted see-saw-like geometry to six Mo and four Se atoms. There are one shorter (2.67 Å) and two longer (2.73 Å) Mo–Mo bond lengths. There are a spread of Mo–Se bond distances ranging from 2.64–2.72 Å. In the third Mo site, Mo is bonded in a distorted see-saw-like geometry to six Mo and four Se atoms. There are a spread of Mo–Se bond distances ranging from 2.64–2.72 Å. In is bonded in a trigonal planar geometry to three Se atoms. All In–Se bond lengths are 3.31 Å. There are three inequivalent Se sites. In the first Se site, Se is bonded in a 5-coordinate geometry to four Mo and one In atom. In the second Se site, Se is bonded in a 5-coordinate geometry to four Mo and one In atom. In the third Se site, Se is bonded in a 5-coordinate geometry to four Mo and one In atom.

36 MATERIALS SCIENCE↗

Materials Data on Tl(MoSe)3 by Materials Project

(MoSe)3Tl crystallizes in the hexagonal P6_3/m space group. The structure is one-dimensional and consists of two ramor molecules and one MoSe ribbon oriented in the (0, 0, 1) direction. In the MoSe ribbon, Mo is bonded in a distorted see-saw-like geometry to six equivalent Mo and four equivalent Se atoms. There are two shorter (2.67 Å) and four longer (2.74 Å) Mo–Mo bond lengths. There are a spread of Mo–Se bond distances ranging from 2.63–2.72 Å. Se is bonded in a 4-coordinate geometry to four equivalent Mo atoms.

36 MATERIALS SCIENCE↗

Electron-phonon coupling induced intrinsic Floquet electronic structure

Floquet states are a topic of intense contemporary interest, which is often induced by coherent external oscillating perturbation (e.g., laser, or microwave) which breaks the continuous time translational symmetry of the systems. Usually, electron–phonon coupling modifies the electronic structure of a crystal as a non-coherent perturbation and seems difficult to form Floquet states. Surprisingly, we found that the thermal equilibrium electron–phonon coupling in M(MoS) 3 and M(MoSe) 3 (where M is a metallic element) exhibits a coherent behavior, and the electronic structure can be described by the Floquet theorem. Such a coherent Floquet state is caused by a selective giant electron–phonon coupling, with thermodynamic phonon oscillation serving as a driving force on the electronic part of the system. The quasi-1D Dirac cone at the Fermi energy has its band gap open and close regularly. Similarly, the electric current will oscillate even under a constant voltage.

36 MATERIALS SCIENCE↗

Synthesis and Electrical Properties of a New Compound (BiSe) 0.97 (Bi 2 Se 3 ) 1.26 (BiSe) 0.97 (MoSe 2 ) Containing Metallic 1T-MoSe 2

The synthesis and electrical properties of a new misfit compound containing BiSe, Bi 2 Se 3 , and MoSe 2 constituent layers are reported. The reaction pathway involves competition between the formation of (BiSe) 1+x (Bi 2 Se 3 ) 1+y (BiSe) 1+x (MoSe 2 ) and [(Bi 2 Se 3 ) 1+y ] 2 (MoSe 2 ). Excess Bi and Se are required in the precursor to synthesize (BiSe) 1+x (Bi 2 Se 3 ) 1+y (BiSe) 1+x (MoSe 2 ). High-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) confirm the stacking sequence of the heterostructure. Small grains of both 2H- and 1T-MoSe 2 are observed in the MoSe 2 layers. X-ray photoelectron spectroscopy (XPS) indicates that there is a significantly higher percentage of 1T-MoSe 2 in (BiSe) 1+x (Bi 2 Se 3 ) 1+y (BiSe) 1+x (MoSe 2 ) than in (BiSe) 0.97 (MoSe 2 ), suggesting that more charge transfer to MoSe 2 occurs due to the additional BiSe layer. The additional charge transfer results in (BiSe) 1+x (Bi 2 Se 3 ) 1+y (BiSe) 1+x (MoSe 2 ) having a low resistivity (14–19 μΩ m) with metallic temperature dependence. Furthermore, the heterogeneous mix of MoSe 2 polytypes observed in the XPS complicates the interpretation of the Hall data as two bands contribute to the electrical continuity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Asymmetric magnetic proximity interactions in MoSe 2 /CrBr 3 van der Waals heterostructures

Magnetic proximity interactions between atomically thin semiconductors and two-dimensional magnets provide a means to manipulate spin and valley degrees of freedom in non-magnetic monolayers, without using applied magnetic fields. In such van der Waals heterostructures, magnetic proximity interactions originate in the nanometre-scale coupling between spin-dependent electronic wavefunctions in the two materials, and typically their overall effect is regarded as an effective magnetic field acting on the semiconductor monolayer. Here we demonstrate that magnetic proximity interactions in van der Waals heterostructures can in fact be markedly asymmetric. Valley-resolved reflection spectroscopy of MoSe2/CrBr3 van der Waals structures reveals strikingly different energy shifts in the K and K' valleys of the MoSe2 due to ferromagnetism in the CrBr3 layer. Density functional calculations indicate that valley-asymmetric magnetic proximity interactions depend sensitively on the spin-dependent hybridization of overlapping bands and as such are likely a general feature of hybrid van der Waals structures. Here, these studies suggest routes to control specific spin and valley states in monolayer semiconductors.

36 MATERIALS SCIENCE↗

The Variation of Hydrocarbon Abundances with Latitude and Season in Saturn's Stratosphere

We have developed a realistic, time-variable, one-dimensional, seasonal model for stratospheric photochemistry on Saturn using the Caltech/ JPL KINETICS code [1,2,3]. The model accounts for variations in ultraviolet flux due to orbital position, solar-cycle variations, and ring-shadowing effects. The results for two Saturnian years, starting at Ls = 0 in 1950 and running until the upcoming northern vernal equinox in 2009, are presented for numerous latitudes. The same two model years are run over and over again until the model convergences to make sure that high-altitude effects have had a chance to propagate down through the atmosphere. We use the SOLAR2000 model [4,5], in combination with the spectra presented in [6], to predict the ultraviolet flux at any wavelength and any point in time during the simulation. Saturn's orbital position during the simulation was taken from the ephemeris calculator at http://ssd.jpl.nasa.gov/horizons.html [7]. The photochemical model is derived from "Model C" of [8] and uses a hydrocarbon reaction list that has been extensively updated from that presented in [3].

Moses, J. I.↗

Efficient computational design of two-dimensional van der Waals heterostructures: Band alignment, lattice mismatch, and machine learning

Here, we develop a computational database, website applications (web-apps), and machine-learning (ML) models to accelerate the design and discovery of two-dimensional (2D) heterostructures. Using density functional theory (DFT) based lattice parameters and electronic band energies for 674 nonmetallic exfoliable 2D materials, we generate 226 779 possible bilayer heterostructures. We classify these heterostructures into type-I, -II, and -III systems according to Anderson’s rule, which is based on the relative band alignments of the noninteracting monolayers. We find that type II is the most common and type III the least common heterostructure type. We subsequently analyze the chemical trends for each heterostructure type in terms of the Periodic Table of constituent elements. The band alignment data can also be used for identifying photocatalysts and high-work-function 2D metals for contacts. We validate our results by comparing them to experimental data as well as hybrid-functional predictions. Additionally, we carry out DFT calculations of a few selected systems (MoS 2 /WSe 2 , MoS 2 /h-BN, and MoSe 2 /CrI 3 ), to compare the band-alignment description with the predictions from Anderson’s rule. We develop web-apps to enable users to virtually create combinations of 2D materials and predict their properties. Additionally, we use ML tools to predict band-alignment information for 2D materials. The web-apps, tools, and associated data will be distributed through the JARVIS-HETEROSTRUCTURE website. Our analysis, results, and the developed web-apps can be applied to the screening and design applications, such as finding alternative photocatalysts, photodetectors, and high-work-function (WF) 2D-metal contacts.

2-dimensional systems↗

Mechanical Characterization of Stacked Single-Crystal of Polyethylene and Monolayer MoSe 2

Polymer single crystal (SC) is a key building block of semicrystalline polymers. However, direct experimental measurement of freestanding mono-lamella polymer SC has not been demonstrated. This is, in large part, due to the difficulties associated with manipulating freestanding individual mono-lamella SC because of its extremely low rigidity and low robustness. Here, we demonstrate a new strategy to successfully suspend and test a polymer SC by using a 2D material as backing. In particular, mono-lamella polyethylene (PE) SC is stacked on monolayer MoSe 2 , and the hybrid stacks can be suspended over microholes. Nanoindentation is used to probe the suspended PE-SC/MoSe2 stacks and MoSe 2 monolayers. The results suggest the first experimentally-measured in-plane moduli of PE-SC and 2D MoSe 2 as 32 ± 3 and 237 ± 15 GPa, respectively. Such a stacked unit represents an ultrathin structure of polymer-ceramic laminate and the idea can be applied to other laminated composite systems. Therefore, this research will pave the way to accurately measure the mechanical properties of polymer SCs and their composites, as well as provide a key insight on designing composite structures.

36 MATERIALS SCIENCE↗

Tuning Exciton Emission via Ferroelectric Polarization at a Heterogeneous Interface between a Monolayer Transition Metal Dichalcogenide and a Perovskite Oxide Membrane

Here we demonstrate the integration of a thin BaTiO 3 (BTO) membrane with monolayer MoSe 2 in a dual gate device that enables in-situ manipulation of the BTO ferroelectric polarization with a voltage pulse. While two-dimensional (2D) transition metal dichalcogenides (TMDs) offer remarkable adaptability, their hybrid integration with other families of functional materials beyond the realm of 2D materials has been challenging. Released functional oxide membranes offer a solution for 2D/3D integration via stacking. 2D TMD excitons can serve as a local probe of the ferroelectric polarization in BTO at a heterogeneous interface. Using photoluminescence (PL) of MoSe 2 excitons to optically readout the doping level, we find that the relative population of charge carriers in MoSe 2 depends sensitively on the ferroelectric polarization. This finding points to a promising avenue for future-generations versatile sensing devices with high sensitivity, fast read-out, and diverse applicability for advanced signal processing.

42 ENGINEERING↗