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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Ab-initio vibrational properties of WTe2 and Li0.5WTe2

We present ab-initio calculations of the Td and 1T’ phases of WTe2 and the Td’ phase of Li 0.5 WTe 2 using density functional theory (DFT). These include lattice relaxations, total energy calculations, phonon calculations, and calculations of elastic constants. We also provide a detailed view of the transformation from Td to Td’ using a non-primitive representation of the Td lattice that more closely resembles the Td’ structure. The details presented here are intended as a supplement to a forthcoming experimental-computational paper on lithiated WTe 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2023

Understanding palladium–tellurium cluster formation on WTe2: From a kinetically hindered distribution to thermodynamically controlled monodispersity

Abstract A fundamental understanding of the transition metal dichalcogenide (TMDC)–metal interface is critical for their utilization in a broad range of applications. We investigate how the deposition of palladium (Pd), as a model metal, on WTe2(001), leads to the assembly of Pd into clusters and nanoparticles. Using X-ray photoemission spectroscopy, scanning tunneling microscopy imaging, and ab initio simulations, we find that Pd nucleation is driven by the interaction with and the availability of mobile excess tellurium (Te) leading to the formation of Pd-Te clusters at room temperature. Surprisingly, the nucleation of Pd-Te clusters is not affected by intrinsic surface defects, even at elevated temperatures. Upon annealing, the Pd-Te nanoclusters adopt an identical nanostructure and are stable up to ∼523 K. Density functional theory calculations provide a foundation for our understanding of the mobility of Pd and Te atoms, preferential nucleation of Pd-Te clusters, and the origin of their annealing-induced monodispersity. These results highlight the role the excess chalcogenide atoms may play in the metal deposition process. More broadly, the discoveries of synthetic pathways yielding thermally robust monodispersed nanostructures on TMDCs are critical to the manufacturing of novel quantum and microelectronics devices and catalytically active nano-alloy centers.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Terahertz response of monolayer and few-layer WTe2 at the nanoscale

Abstract Tungsten ditelluride (WTe 2 ) is an atomically layered transition metal dichalcogenide whose physical properties change systematically from monolayer to bilayer and few-layer versions. In this report, we use apertureless scattering-type near-field optical microscopy operating at Terahertz (THz) frequencies and cryogenic temperatures to study the distinct THz range electromagnetic responses of mono-, bi- and trilayer WTe 2 in the same multi-terraced micro-crystal. THz nano-images of monolayer terraces uncovered weakly insulating behavior that is consistent with transport measurements. The near-field signal on bilayer regions shows moderate metallicity with negligible temperature dependence. Subdiffractional THz imaging data together with theoretical calculations involving thermally activated carriers favor the semimetal scenario with $$\Delta \approx -10\,{{{\rm{meV}}}}$$ Δ ≈ − 10 meV over the semiconductor scenario for bilayer WTe 2 . Also, we observed clear metallic behavior of the near-field signal on trilayer regions. Our data are consistent with the existence of surface plasmon polaritons in the THz range confined to trilayer terraces in our specimens. Finally, data for microcrystals up to 12 layers thick reveal how the response of a few-layer WTe 2 asymptotically approaches the bulk limit.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Nanoscale studies of electric field effects on monolayer 1T′-WTe2

Abstract Monolayer 1 T′-WTe 2 is a quantum spin Hall insulator with a gapped 2D-bulk and gapless helical edge states persisting to temperatures ~100 K. Despite the far-ranging interest, the magnitude of the bulk gap, the effect of gating on the 2D-band structure, as well the role interactions are not established. In this work we use STM spectroscopy to measure the intrinsic bulk gap of monolayer 1 T′-WTe 2 and show that gate induced electric fields cause large changes of the gap magnitude. Our first-principles DFT-derived tight-binding model reveal that a combination of spatial localization of the conduction and valance bands and Rashba-like spin-orbit coupling leads to a gating induced spin-splitting of the 2D-bulk bands in the tens of meV, thereby reducing the band gap. Our work explains the large sensitivity of the band structure to electric fields and suggests a new avenue for realizing proximity induced non-trivial superconductivity in monolayer 1 T′-WTe 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2020

Magnetic proximity and nonreciprocal current switching in a monolayer WTe2 helical edge

The integration of diverse electronic phenomena, such as magnetism and nontrivial topology, into a single system is normally studied either by seeking materials that contain both ingredients, or by layered growth of contrasting materials. The ability to simply stack very different two-dimensional van der Waals materials in intimate contact permits a different approach. Here we use this approach to couple the helical edges states in a two-dimensional topological insulator, monolayer WTe 2 , to a two-dimensional layered antiferromagnet, CrI 3 . We find that the edge conductance is sensitive to the magnetization state of the CrI 3 , and the coupling can be understood in terms of an exchange field from the nearest and next-nearest CrI 3 layers that produces a gap in the helical edge. We also find that the nonlinear edge conductance depends on the magnetization of the nearest CrI 3 layer relative to the current direction. At low temperatures this produces an extraordinarily large nonreciprocal current that is switched by changing the antiferromagnetic state of the CrI 3 .

36 MATERIALS SCIENCE↗
DOE OSTI2020

Proximity-induced superconducting gap in the quantum spin Hall edge state of monolayer WTe2

The quantum spin Hall insulator is characterized by a bandgap in the two-dimensional (2D) interior and helical 1D edge states 1 , 2 , 3 . Inducing superconductivity in the helical edge state results in a 1D topological superconductor, a highly sought-after state of matter at the core of many proposals for topological quantum computing 4 . In the present study, we report the coexistence of superconductivity and the quantum spin Hall edge state in a van der Waals heterostructure, by placing a monolayer of 1T'-WTe 2 , a quantum spin Hall insulator 1 , 2 , 3 , on a van der Waals superconductor, NbSe 2 . Using scanning tunnelling microscopy and spectroscopy (STM/STS), we demonstrate that the WTe 2 monolayer exhibits a proximity-induced superconducting gap due to the underlying superconductor and that the spectroscopic features of the quantum spin Hall edge state remain intact. Taken together, these observations provide conclusive evidence for proximity-induced superconductivity in the quantum spin Hall edge state in WTe 2 , a crucial step towards realizing 1D topological superconductivity and Majorana bound states in this van der Waals material platform.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Materials Data on Te2Mo2WSe4 by Materials Project

WTe2(MoSe2)2 is Molybdenite-derived structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of two MoSe2 sheets oriented in the (0, 0, 1) direction and one WTe2 sheet oriented in the (0, 0, 1) direction. In each MoSe2 sheet, Mo+4.50+ is bonded to six equivalent Se2- atoms to form distorted edge-sharing MoSe6 pentagonal pyramids. There are three shorter (2.56 Å) and three longer (2.57 Å) Mo–Se bond lengths. Se2- is bonded in a 3-coordinate geometry to three equivalent Mo+4.50+ atoms. In the WTe2 sheet, W3+ is bonded to six Te2- atoms to form distorted edge-sharing WTe6 pentagonal pyramids. All W–Te bond lengths are 2.72 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 12-coordinate geometry to three equivalent W3+ atoms. In the second Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent W3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te2Mo2WSe4 by Materials Project

WTe2(MoSe2)2 is Molybdenite-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is two-dimensional and consists of two MoSe2 sheets oriented in the (0, 0, 1) direction and one WTe2 sheet oriented in the (0, 0, 1) direction. In each MoSe2 sheet, Mo+4.50+ is bonded to six equivalent Se2- atoms to form distorted edge-sharing MoSe6 pentagonal pyramids. There are three shorter (2.56 Å) and three longer (2.57 Å) Mo–Se bond lengths. Se2- is bonded in a 3-coordinate geometry to three equivalent Mo+4.50+ atoms. In the WTe2 sheet, W3+ is bonded to six equivalent Te2- atoms to form distorted edge-sharing WTe6 pentagonal pyramids. All W–Te bond lengths are 2.72 Å. Te2- is bonded in a 12-coordinate geometry to three equivalent W3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te2W3S4 by Materials Project

WTe2(WS2)2 is Molybdenite-derived structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of two WS2 sheets oriented in the (0, 0, 1) direction and one WTe2 sheet oriented in the (0, 0, 1) direction. In each WS2 sheet, W4+ is bonded to six S2- atoms to form distorted edge-sharing WS6 pentagonal pyramids. All W–S bond lengths are 2.45 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent W4+ atoms. In the second S2- site, S2- is bonded in a 3-coordinate geometry to three equivalent W4+ atoms. In the WTe2 sheet, W4+ is bonded to six Te2- atoms to form distorted edge-sharing WTe6 pentagonal pyramids. All W–Te bond lengths are 2.71 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 12-coordinate geometry to three equivalent W4+ atoms. In the second Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent W4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te4Mo(WSe)2 by Materials Project

(WTe2)2MoSe2 is Molybdenite-derived structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of one MoSe2 sheet oriented in the (0, 0, 1) direction and two WTe2 sheets oriented in the (0, 0, 1) direction. In the MoSe2 sheet, Mo6+ is bonded to six Se2- atoms to form distorted edge-sharing MoSe6 pentagonal pyramids. All Mo–Se bond lengths are 2.58 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Mo6+ atoms. In the second Se2- site, Se2- is bonded in a distorted T-shaped geometry to three equivalent Mo6+ atoms. In each WTe2 sheet, W3+ is bonded to six equivalent Te2- atoms to form distorted edge-sharing WTe6 pentagonal pyramids. All W–Te bond lengths are 2.73 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent W3+ atoms. All Te–W bond lengths are 2.73 Å. In the second Te2- site, Te2- is bonded in a 12-coordinate geometry to three equivalent W3+ atoms. All Te–W bond lengths are 2.73 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te6Mo2W by Materials Project

WTe2(MoTe2)2 is Molybdenite-derived structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of two MoTe2 sheets oriented in the (0, 0, 1) direction and one WTe2 sheet oriented in the (0, 0, 1) direction. In each MoTe2 sheet, Mo+4.50+ is bonded to six equivalent Te2- atoms to form distorted edge-sharing MoTe6 pentagonal pyramids. All Mo–Te bond lengths are 2.74 Å. Te2- is bonded in a 3-coordinate geometry to three equivalent Mo+4.50+ atoms. In the WTe2 sheet, W3+ is bonded to six equivalent Te2- atoms to form distorted edge-sharing WTe6 pentagonal pyramids. All W–Te bond lengths are 2.74 Å. Te2- is bonded in a 3-coordinate geometry to three equivalent W3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te4Mo(WSe)2 by Materials Project

(WTe2)2MoSe2 is Molybdenite-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is two-dimensional and consists of one MoSe2 sheet oriented in the (0, 0, 1) direction and two WTe2 sheets oriented in the (0, 0, 1) direction. In the MoSe2 sheet, Mo6+ is bonded to six equivalent Se2- atoms to form distorted edge-sharing MoSe6 pentagonal pyramids. All Mo–Se bond lengths are 2.58 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent Mo6+ atoms. In each WTe2 sheet, W3+ is bonded to six Te2- atoms to form distorted edge-sharing WTe6 pentagonal pyramids. All W–Te bond lengths are 2.73 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded in a 3-coordinate geometry to three equivalent W3+ atoms. In the second Te2- site, Te2- is bonded in a 12-coordinate geometry to three equivalent W3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te6Mo2W by Materials Project

WTe2(MoTe2)2 is Molybdenite-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is two-dimensional and consists of two MoTe2 sheets oriented in the (0, 0, 1) direction and one WTe2 sheet oriented in the (0, 0, 1) direction. In each MoTe2 sheet, Mo+4.50+ is bonded to six equivalent Te2- atoms to form distorted edge-sharing MoTe6 pentagonal pyramids. All Mo–Te bond lengths are 2.74 Å. Te2- is bonded in a 3-coordinate geometry to three equivalent Mo+4.50+ atoms. In the WTe2 sheet, W3+ is bonded to six equivalent Te2- atoms to form distorted edge-sharing WTe6 pentagonal pyramids. All W–Te bond lengths are 2.74 Å. Te2- is bonded in a 3-coordinate geometry to three equivalent W3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te2Mo2WS4 by Materials Project

WTe2(MoS2)2 is Molybdenite-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is two-dimensional and consists of two MoS2 sheets oriented in the (0, 0, 1) direction and one WTe2 sheet oriented in the (0, 0, 1) direction. In each MoS2 sheet, Mo+4.50+ is bonded to six S2- atoms to form distorted edge-sharing MoS6 pentagonal pyramids. All Mo–S bond lengths are 2.45 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent Mo+4.50+ atoms. In the second S2- site, S2- is bonded in a 3-coordinate geometry to three equivalent Mo+4.50+ atoms. In the WTe2 sheet, W3+ is bonded to six equivalent Te2- atoms to form distorted edge-sharing WTe6 pentagonal pyramids. All W–Te bond lengths are 2.71 Å. Te2- is bonded in a 12-coordinate geometry to three equivalent W3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te4W3S2 by Materials Project

(WTe2)2WS2 is Molybdenite-derived structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of one WS2 sheet oriented in the (0, 0, 1) direction and two WTe2 sheets oriented in the (0, 0, 1) direction. In the WS2 sheet, W4+ is bonded to six S2- atoms to form distorted edge-sharing WS6 pentagonal pyramids. All W–S bond lengths are 2.48 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 3-coordinate geometry to three equivalent W4+ atoms. In the second S2- site, S2- is bonded in a distorted T-shaped geometry to three equivalent W4+ atoms. In each WTe2 sheet, W4+ is bonded to six equivalent Te2- atoms to form distorted edge-sharing WTe6 pentagonal pyramids. All W–Te bond lengths are 2.72 Å. Te2- is bonded in a 3-coordinate geometry to three equivalent W4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Te6MoW2 by Materials Project

(WTe2)2MoTe2 is Molybdenite-derived structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of one MoTe2 sheet oriented in the (0, 0, 1) direction and two WTe2 sheets oriented in the (0, 0, 1) direction. In the MoTe2 sheet, Mo6+ is bonded to six equivalent Te2- atoms to form distorted edge-sharing MoTe6 pentagonal pyramids. All Mo–Te bond lengths are 2.74 Å. Te2- is bonded in a 3-coordinate geometry to three equivalent Mo6+ atoms. In each WTe2 sheet, W3+ is bonded to six equivalent Te2- atoms to form distorted edge-sharing WTe6 pentagonal pyramids. All W–Te bond lengths are 2.74 Å. Te2- is bonded in a 3-coordinate geometry to three equivalent W3+ atoms.

36 MATERIALS SCIENCE↗