Search NASA⌕ Search

SEARCH · Search NASA

Results for “TaSe2”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

17 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on K2(TaSe2)3 by Materials Project

K3(TaSe2)4K(TaSe2)2 crystallizes in the hexagonal P-6m2 space group. The structure is two-dimensional and consists of one K(TaSe2)2 sheet oriented in the (0, 0, 1) direction and one K3(TaSe2)4 sheet oriented in the (0, 0, 1) direction. In the K(TaSe2)2 sheet, K1+ is bonded in a 12-coordinate geometry to six equivalent Se2- atoms. All K–Se bond lengths are 3.21 Å. Ta+3.33+ is bonded to six Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. There are three shorter (2.62 Å) and three longer (2.64 Å) Ta–Se bond lengths. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three equivalent K1+ and three equivalent Ta+3.33+ atoms to form a mixture of distorted corner, edge, and face-sharing SeK3Ta3 octahedra. The corner-sharing octahedral tilt angles are 38°. In the second Se2- site, Se2- is bonded in a distorted T-shaped geometry to three equivalent Ta+3.33+ atoms. In the K3(TaSe2)4 sheet, there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 12-coordinate geometry to six Se2- atoms. There are three shorter (3.20 Å) and three longer (3.22 Å) K–Se bond lengths. In the second K1+ site, K1+ is bonded in a 12-coordinate geometry to six equivalent Se2- atoms. All K–Se bond lengths are 3.22 Å. There are two inequivalent Ta+3.33+ sites. In the first Ta+3.33+ site, Ta+3.33+ is bonded to six Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. There are three shorter (2.62 Å) and three longer (2.64 Å) Ta–Se bond lengths. In the second Ta+3.33+ site, Ta+3.33+ is bonded to six Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. All Ta–Se bond lengths are 2.63 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a distorted T-shaped geometry to three equivalent Ta+3.33+ atoms. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to three equivalent K1+ and three equivalent Ta+3.33+ atoms. In the third Se2- site, Se2- is bonded to three equivalent K1+ and three equivalent Ta+3.33+ atoms to form a mixture of distorted corner, edge, and face-sharing SeK3Ta3 octahedra. The corner-sharing octahedral tilt angles are 37°. In the fourth Se2- site, Se2- is bonded to three equivalent K1+ and three equivalent Ta+3.33+ atoms to form a mixture of distorted corner, edge, and face-sharing SeK3Ta3 octahedra. The corner-sharing octahedral tilt angles are 37°.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Dimensionality-driven metal to Mott insulator transition in two-dimensional 1T-TaSe2

Abstract Two-dimensional materials represent a major frontier for research into exotic many-body quantum phenomena. In the extreme two-dimensional limit, electron-electron interaction often dominates over other electronic energy scales, leading to strongly correlated effects such as quantum spin liquid and unconventional superconductivity. The dominance is conventionally attributed to the lack of electron screening in the third dimension. Here, we discover an intriguing metal to Mott insulator transition in 1T-TaSe2 that defies conventional wisdom. Specifically, we find that dimensionality crossover, instead of reduced screening, drives the transition in atomically thin 1T-TaSe2. A dispersive band crossing the Fermi level is found to be responsible for the bulk metallicity in the material. Reducing the dimensionality, however, effectively quenches the kinetic energy of these initially itinerant electrons, and drives the material into a Mott insulating state. The dimensionality-driven metal to Mott insulator transition resolves the long-standing dichotomy between metallic bulk and insulating surface of 1T-TaSe2. Our work further reveals a new pathway for modulating two-dimensional materials that enables exploring strongly correlated systems across uncharted parameter space.

1T-TaSe2↗
DOE OSTI2020

Materials Data on TaSe2 by Materials Project

TaSe2 is trigonal omega structured and crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of one TaSe2 sheet oriented in the (0, 0, 1) direction. Ta4+ is bonded to six equivalent Se2- atoms to form edge-sharing TaSe6 octahedra. All Ta–Se bond lengths are 2.61 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent Ta4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaSe2 by Materials Project

TaSe2 is Molybdenite-like structured and crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of six TaSe2 sheets oriented in the (0, 0, 1) direction. Ta4+ is bonded to six equivalent Se2- atoms to form edge-sharing TaSe6 octahedra. All Ta–Se bond lengths are 2.61 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent Ta4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaSe2 by Materials Project

TaSe2 is Molybdenite-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is two-dimensional and consists of two TaSe2 sheets oriented in the (0, 0, 1) direction. Ta4+ is bonded to six equivalent Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. All Ta–Se bond lengths are 2.62 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent Ta4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaSe2 by Materials Project

TaSe2 is Molybdenite-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is two-dimensional and consists of four TaSe2 sheets oriented in the (0, 0, 1) direction. Ta4+ is bonded to six equivalent Se2- atoms to form edge-sharing TaSe6 octahedra. All Ta–Se bond lengths are 2.61 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent Ta4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaSe2 by Materials Project

TaSe2 is trigonal omega-like structured and crystallizes in the trigonal R-3m space group. The structure is two-dimensional and consists of three TaSe2 sheets oriented in the (0, 0, 1) direction. Ta4+ is bonded to six equivalent Se2- atoms to form edge-sharing TaSe6 octahedra. All Ta–Se bond lengths are 2.61 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent Ta4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaSe2 by Materials Project

TaSe2 is Molybdenite-like structured and crystallizes in the hexagonal P-6m2 space group. The structure is two-dimensional and consists of four TaSe2 sheets oriented in the (0, 0, 1) direction. Ta4+ is bonded to six equivalent Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. All Ta–Se bond lengths are 2.62 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent Ta4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaSe2 by Materials Project

TaSe2 is Molybdenite-like structured and crystallizes in the trigonal R3m space group. The structure is two-dimensional and consists of three TaSe2 sheets oriented in the (0, 0, 1) direction. Ta4+ is bonded to six Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. All Ta–Se bond lengths are 2.62 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Ta4+ atoms. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Ta4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaSe2 by Materials Project

TaSe2 is Molybdenite-like structured and crystallizes in the hexagonal P6_3mc space group. The structure is two-dimensional and consists of four TaSe2 sheets oriented in the (0, 0, 1) direction. Ta4+ is bonded to six equivalent Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. All Ta–Se bond lengths are 2.62 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent Ta4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaSe2 by Materials Project

TaSe2 is Molybdenite-like structured and crystallizes in the orthorhombic Fmm2 space group. The structure is two-dimensional and consists of two TaSe2 sheets oriented in the (0, 0, 1) direction. Ta4+ is bonded to six Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. All Ta–Se bond lengths are 2.62 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Ta4+ atoms. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Ta4+ atoms. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Ta4+ atoms. In the fourth Se2- site, Se2- is bonded in a distorted T-shaped geometry to three equivalent Ta4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaSe2 by Materials Project

TaSe2 is Molybdenite structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is two-dimensional and consists of two TaSe2 sheets oriented in the (0, 0, 1) direction. Ta4+ is bonded to six equivalent Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. All Ta–Se bond lengths are 2.61 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent Ta4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Precision-controlled ultrafast electron microscope platforms. A case study: Multiple-order coherent phonon dynamics in 1T-TaSe2 probed at 50 fs–10 fm scales

We report on the first detailed beam tests attesting the fundamental principle behind the development of high-current-efficiency ultrafast electron microscope systems where a radio frequency (RF) cavity is incorporated as a condenser lens in the beam delivery system. To allow for the experiment to be carried out with a sufficient resolution to probe the performance at the emittance floor, a new cascade loop RF controller system is developed to reduce the RF noise floor. Temporal resolution at 50 fs in full-width-at-half-maximum and detection sensitivity better than 1% are demonstrated on exfoliated 1T-TaSe2 system under a moderate repetition rate. To benchmark the performance, multi-terahertz edge-mode coherent phonon excitation is employed as the standard candle. The high temporal resolution and the significant visibility to very low dynamical contrast in diffraction signals via high-precision phase-space manipulation give strong support to the working principle for the new high-brightness femtosecond electron microscope systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Controlling structure and interfacial interaction of monolayer TaSe2 on bilayer graphene

Abstract Tunability of interfacial effects between two-dimensional (2D) crystals is crucial not only for understanding the intrinsic properties of each system, but also for designing electronic devices based on ultra-thin heterostructures. A prerequisite of such heterostructure engineering is the availability of 2D crystals with different degrees of interfacial interactions. In this work, we report a controlled epitaxial growth of monolayer TaSe 2 with different structural phases, 1 H and 1 T , on a bilayer graphene (BLG) substrate using molecular beam epitaxy, and its impact on the electronic properties of the heterostructures using angle-resolved photoemission spectroscopy. 1 H -TaSe 2 exhibits significant charge transfer and band hybridization at the interface, whereas 1 T -TaSe 2 shows weak interactions with the substrate. The distinct interfacial interactions are attributed to the dual effects from the differences of the work functions as well as the relative interlayer distance between TaSe 2 films and BLG substrate. The method demonstrated here provides a viable route towards interface engineering in a variety of transition-metal dichalcogenides that can be applied to future nano-devices with designed electronic properties.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta2In(ReSe4)2 by Materials Project

TaSe2TaInSe2(ReSe2)2 is Molybdenite-derived structured and crystallizes in the trigonal P3m1 space group. The structure is two-dimensional and consists of two ReSe2 sheets oriented in the (0, 0, 1) direction; one TaInSe2 sheet oriented in the (0, 0, 1) direction; and one TaSe2 sheet oriented in the (0, 0, 1) direction. In each ReSe2 sheet, Re3+ is bonded to six Se2- atoms to form distorted edge-sharing ReSe6 pentagonal pyramids. There are three shorter (2.53 Å) and three longer (2.54 Å) Re–Se bond lengths. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a distorted T-shaped geometry to three equivalent Re3+ atoms. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Re3+ atoms. In the TaInSe2 sheet, Ta+4.50+ is bonded to six Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. There are three shorter (2.61 Å) and three longer (2.62 Å) Ta–Se bond lengths. In1+ is bonded in a 6-coordinate geometry to three equivalent Se2- atoms. All In–Se bond lengths are 3.16 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to three equivalent Ta+4.50+ atoms. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to three equivalent Ta+4.50+ and three equivalent In1+ atoms. In the TaSe2 sheet, Ta+4.50+ is bonded to six equivalent Se2- atoms to form distorted edge-sharing TaSe6 pentagonal pyramids. All Ta–Se bond lengths are 2.61 Å. Se2- is bonded in a 3-coordinate geometry to three equivalent Ta+4.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Quantization of the band at the surface of charge density wave material 2H-TaSe 2

By using angle-resolved photoemission spectroscopy combined with the first-principles electronics atructure calculations, we report the quantum well states at the surface of a single crystal 2H-TaSe 2 . We observed sub-bands at the three-dimensional Brillouin zone center forming the quantized states due to its highly dispersive nature and light effective mass along k z direction. The quantized sub-bands shift upward towards E F with the decrease of temperature across TCDW. The band shift could not be explained by two-dimensional Fermi-surface nesting-driven charge density waves(CDW), nor by purely strong electron-phonon coupling only. The CDW in 2H-TaSe 2 is likely related to the bands at higher binding energy, and the CDW mechanism could be explained by the excitons, and our observation gives support to this scenario.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗