The layered transition metal dichalcogenide compounds 1T-TaS2 and 4H-TaS2 are well known for their exotic properties, which include charge density wave, superconductivity, Mott transition, etc., and ...lately quantum spin liquid. Here, we report the magnetic, transport and transmission electron microscopy study of the charge density wave and superconductivity in 6R-TaS2 which is a relatively less studied polymorph of this dichalcogenide TaS2. Our high temperature electron microscopy reveals multiple charge density wave transitions between room temperature and 660K. Magnetization, and the electrical resistivity measurements in the temperature range of 2-400 K reveal that 6R-TaS2 undergoes a charge density wave transition around 305 K and is followed by a transition to a superconducting state around 3.5 K. The low temperature specific heat measurement exhibits anomaly associated with the superconducting transition around 2.4 K. The estimated Ginzburg Landau parameter suggests that this compound lies at the extreme limit of type-II superconductivity.
A plasma oxidation method is developed to fabricate atomic‐scale pores in the basal planes of electrochemically inert TaS2 nanosheets to functionalize the 2D crystals with high electrocatalysis for ...hydrogen evolution reaction. Quantitative measurements of under‐coordinated atoms at edges of the pores by aberration‐corrected transmission electron microscopy reveal the intrinsic correlation between the defective atomic sites and electrocatalytic activities of 2D TaS2.
Complicated charge density wave (CDW) phases transitions in the transition-metal dichalcogenide (TMDs) 1T-TaS2 have attracted wide research interest owing to the accompanied complex electronic ...structure transition which has not been fully understood. Inspired by a recent experimental work (Zhao et al. (2020), reported the successful preparation of Ta atom self-intercalated 2H-TaS2), we employed first-principles methods to investigate Ta atom self-intercalated 1T-TaS2, exploring effects of self-intercalation on electronic structure, magnetism, and stability ofthe charge density wave (CDW) phase in 1T-TaS2. Our first-principle calculation shows that the intercalation of Ta atom into the van der Waals gap of 1T-TaS2 induce the phase transition from 1T phase to CDW phase, and the positions of intercalated Ta atom determine the distribution of David-star clusters. Accompanied by the structural phase transition, the Ta intercalated 1T-TaS2 also undergoes an electronic structure phase transition from non-magnetic metal to half-metal which is also different from conventional charge density wave’s insulating state. When appropriate holes are doped to the intercalation system, the CDW David-star cluster is gradually destroyed and eventually returns to its original 1T phase. Our studies enrich the phase diagram of TaS2 and highlight the effective manipulation of the CDW states via self-intercalation. This type of materials may have very promising applications in future electronic devices.
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•The intrinsic 1T-TaS2 is a metallic material without band gap.•When the torsion angle reaches 10°, we found a narrow split-off band above the Fermi level.•The torsion causes a significant increase ...in the static dielectric constant.•When the torsion angle reaches 18°, the electronic structure and optical constants change significantly due to the fracture of original bonds.
The optoelectronic properties of monolayer 1T-TaS2 at 0∼20° torsion are systematically studied, including the band structure, density of electronic states, complex dielectric function, absorption and reflection spectra based on first-principles calculations. We found that a split-off bandgap above the Fermi level by torsional deformation and increases with torsion. The analysis of the optical properties reveals that the static dielectric constant, absorption peak, and reflection peak in the low-energy region increases with torsion. When the torsion angle reaches 18°, the electronic structure and optical constants change significantly due to the fracture of original bonds. This paper provides a theoretical reference for the subsequent application of single-layer 1T-TaS2 in the sensor design.
The conductive monolayer 1T TaS2 is a promising candidate to promote spintronic devices to the next level. Through first-principle calculations, we demonstrate that the intrinsic spin Hall ...conductivity (ISHC) in conductive monolayer 1T TaS2 and its interfaces with graphene can be engineered by strain through manipulating the orbital texture of the material. First, we quantitatively study orbital hybridization in monolayer TaS2 under compressive and tensile strains. Next, by calculating the spin Berry curvature (SBC) of the bands over the whole BZ, we investigate the spin Hall conductivity of the pristine and strained monolayer TaS2. With a detailed analysis of the band structure and characterizing the change in the concavity of the bands in the vicinity of the Fermi level, we identify the responsible features for the tunable ISHC to be hybridization strength in conjugation with spin–orbit coupling (SOC). Furthermore, our SBC projected band structure calculations point toward an interesting correlation between the magnitude of the ISHC and the pd hybridization strength. Inspired by the correlation between orbital hybridization and ISHC values, we next look at the heterostructure of graphene and monolayer TaS2. Our calculations show that upon orbital mixing between the two materials, a large ISHC of 235ħeΩ−1cm−1 can be realized which is comparable to many pioneering materials with spintronic applications. These findings suggest possible routes to design novel materials for spintronic application via engineering the orbital texture of the bands.
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•The micro-chemical environments of TaS2 laminates were modified for acid recovery.•Positively charged polymers were inserted into TaS2 channels.•The modified TaS2 membranes show improving acid ...fluxes and separation factors synergistically.•The next generation acid recovery membranes were successfully established.
Two dimensional (2D) TaS2 laminates have highly regular and ordered transfer mass channels, thus being promising acid recovery membrane candidates for diffusion dialysis (DD) applications to discern H+ and metallic ions. However, it remains a daunting task to get access to high-performance 2D acid recycling membranes made from single TaS2 nanosheets. Here, we report manipulation of the chemical environments of TaS2 channels to develop excellent acid recycling 2D membranes. As demonstration projects, positively charged poly(diallyldimethylammonium chloride) (PDDA) and poly(4-vinylpyridine) (P4VP) in acid solution were chosen as polycation intercalators to modify the TaS2 2D channels. Under the DD mode, the TaS2 membrane exhibits a H+ dialysis coefficient (UH+) of 3.72 × 10−3 m h−1 and separation factor (S) of 9 towards the simulated acid pickle. In contrast, the UH+ and S value of the PDDA@TaS2 membrane improve to 12.7 × 10−3 m h−1 and 34.4 respectively. Those of the P4VP@TaS2 membrane increase to 12.5 × 10−3 m h−1 and 29.1 respectively. The reported acid recovery properties of PDDA@TaS2 and P4VP@TaS2 membranes exceed the commercial DF-120 acid recovery membranes. The experiment and simulation results reveal that the synergistical enhancements of UH+ and S originate from the incorporating polycations in PDDA@TaS2 and P4VP@TaS2 composite channels.
Ultrathin two‐dimensional (2D) charge density wave (CDW) materials, with sharp resistance change at the phase‐transition temperature, yet with ultrathin thickness, hold great potential for electrical ...device applications. However, chemical synthesis of high‐quality samples and observation of the CDW states down to the monolayer limit is still of great challenge. Chemical vapor deposition of 1T‐TaS2 sheets on hexagonal boron nitride (h‐BN) with robust CDW states even down to the monolayer extreme is reported here. Further, based on the near commensurate CDW to incommensurate CDW phase transition with a high temperature coefficient of resistance (TCR), highly responsive room‐temperature bolometers are fabricated by suspending the as‐grown 1T‐TaS2 sheets.
Observation of charge density wave (CDW) states at the monolayer limit is of great challenge. By using hexagonal boron nitride as a substrate, chemical vapor deposition of atomically thin 1T‐TaS2 sheets and observation of CDW phase transitions down to the monolayer extreme are achieved. Further, highly bolometric responsivity is demonstrated on 1T‐TaS2 sheets.
As electromagnetic technology advances and demand for electronic devices grows, concerns about electromagnetic pollution intensify. This has spurred focused research on innovative electromagnetic ...absorbers, particularly chalcogenides, noted for their superior absorption capabilities. In this study, we successfully synthesize 3R–TaS2 nanosheets using a straightforward calcination method for the first time. These nanosheets exhibit significant absorption capabilities in both the C-band (4–8 GHz) and Ku-band (12–18 GHz) frequency ranges. By optimizing the calcination process, the complex permittivity of TaS2 is enhanced, specifically for those synthesized at 1000 °C for 24 h. The nanosheets possess dual-band absorption properties, with a notable minimum reflection loss (RLmin) of −41.4 dB in the C-band, and an average absorption intensity exceeding 10 dB in C- and Ku-bands, in the absorbers with a thickness of 5.6 mm. Additionally, the 3R–TaS2 nanosheets are demonstrated to have an effective absorption bandwidth of 5.04 GHz (3.84–8.88 GHz) in the absorbers with thicknesses of 3.5–5.5 mm. The results highlight the multiple reflection effects in 3R–TaS2 as caused by their stacked structures, which could be promising low-frequency absorbers.
Superior charge separation and adsorptive capacity made TiO2/TaS2 a good candidate in the photocatalytic field, and O2− was proved to be the main active radical in the photodegradation of gaseous ...acetaldehyde
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•The introduction of TaS2 was beneficial for the efficient separation of electron-hole pairs.•Compared with bare P25, P25/TaS2 exhibited superior adsorptive capacity.•O2− played the predominant role while OH was the secondary one for the photodegradation of gaseous acetaldehyde.•This work created the pioneer of the application of TaS2 in the photocatalytic field.
Differing from the photocatalysis of liquid contaminant, the capture of gaseous molecule is an essential factor on the photocatalytic activity because of the fast and random motion of gaseous molecule. TaS2 is a two-dimensional material with good conductivity and large specific area, which are beneficial to the adsorption of gaseous pollutant and the separation of photo-induced e−-h+ pairs. Here, P25/TaS2 (P25: commercial TiO2) was synthesized for the first time to explore the effect of the addition of TaS2 on the photocatalytic degradation of gaseous acetaldehyde. It turned out that the existence of TaS2 provided two merits: on the one side, the adsorptive capacity of P25/TaS2 for gaseous acetaldehyde boosted greatly with the highest adsorptive amount of 234.4 mL, which was three times of that of P25 (76.4 mL); on the other side, the separation efficiency of e−-h+ pairs of P25/TaS2 also increased extremely with the highest photo-current response of 15.5 μA/cm2, which was almost four times of that of P25 (4.2 μA/cm2). These two merits made P25/TaS2 have superior photocatalytic activity for the degradation of gaseous acetaldehyde with the highest removal ratio of 98%, which was twice of that of P25 (48%). The cyclic experiments verified that P25/TaS2 could keep excellent cycling stability after 6 cycles usage. In addition, proved by electron spin resonance (ESR) analyses and radicals quenching tests, superoxide radical was the decisive active species for the degradation of gaseous acetaldehyde compared with hydroxyl radical. Briefly, this work not only created the pioneer of the application of TaS2 in the photocatalytic field but also verified TaS2 an efficient co-catalyst in gaseous photocatalysis.
• Growth of Cu-intercalated Ta1+yS2 crystals by the chemical vapour transport method.• Transformation of 2H-CuxTa1+yS2 polytype to 6R-CuxTa1+yS2 polytype.• Influence of crystal grows regimes on the ...structure of CuxTa1+yS2.• Transport measurements of CuxTa1+yS2.
Ta1+yS2 and Cu-intercalated Ta1+yS2 crystals with high Cu concentration were grown by the chemical vapour transport method with different crystal growth regimes. Depending on the cooling process either 2H-type or 6R-type CuxTa1+yS2 crystals were grown. Transformation of 2H-CuxTa1+yS2 polytype crystals to 6R-CuxTa1+yS2 takes place during a low cooling process, whereas during air quenching 2H-type crystals result. It was shown that cooling process and additional annealing steps in crystal growth regimes have an essential influence on the structure of the samples and their physical properties such as superconductivity. The samples were examined by X-ray diffraction, energy dispersive X-ray spectroscopy and electrical resistivity measurements.
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