Strain-induced phonon shifts in tungsten disulfide nanoplatelets and nanotubes

Wang, Fang; Kinloch, Ian A.; Wolverson, Daniel; Tenne, Reshef; Zak, Alla; O’Connell, Eoghan; Bangert, U.; Young, Robert J.

doi:10.1088/2053-1583/4/1/015007

Cited by 104 publications

(100 citation statements)

References 76 publications

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“…Peaks in the Raman spectrum of the untreated WS 2 sample in Figure a can be assigned to the in‐plane E 2G mode at ≈352 cm −1 and to the out‐of‐plane A 1G mode at ≈417 cm −1 of crystalline WS 2 . Consistent with a previous report by Wang et al on WS 2 nanotubes, after laser treatment, the E 2G peak was observed at 351 cm −1 , a softening of the band that is attributable to the increase in lateral size. In contrast, a stiffening of the A 1G mode was observed (peak shifted to 418.5 cm −1 ), consistent with previous reports and indicative of increased thickness, which may be due to the agglomeration of the rods and their attachment through weak van der Waal forces when drop cast for analysis.…”

Section: Resultssupporting

confidence: 92%

Laser‐Directed Assembly of Nanorods of 2D Materials

Ibrahim

Novodchuk

Mistry

et al. 2019

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transparency thus connected networks of 1D nanomaterials [5] have been studied as a viable alternative to thin films of indium tin oxide, which suffer from drawbacks such as brittleness and indium scarcity. [6] Materials such as graphene and transition metal dichalcogenides (TMDs) exhibit excellent electrical properties due to their "flat" 2D chemical structure. Sheets or flakes of these materials can allow for large area coverage with high conductivity but typically at the expense of transparency. [7,8] An approach to improving transparency is utilizing these materials in 1D nanorod-like structures. Carbon nanotubes (CNTs) are the most popular 1D variant of graphene and have been utilized to form large area conducting films, although challenges remain with respect to their purification [9,10] and aggregation. [5] As an alternative to CNTs, the synthesis of carbon-based nanorods has been reported by utilizing arc discharge [11] and microwave plasma chemical vapor deposition (CVD) [12] methods. However, the arc discharge method requires an extensive filtering (Soxhlet extraction) and drying process, while the CVD method requires a high power and temperature (e.g., 850 °C). The growth of graphene nanoribbons has also been reported by ultrahigh vacuum thermal evaporation [13] and hydrothermal techniques, [14] yielding lengths of 20-450 nm and widths of 2-40 nm.In regards to TMDs, molybdenum disulfide (MoS 2 ) nanorods have been synthesized via a redox reaction in an aqueous solution (yielding a nanorod mixture of binary oxides (Mo x O y ) and binary sulfides (Mo x S y )), [15] hydrothermal synthesis, [16] and hydrothermal synthesis of MoO 3 nanorods combined with sulfurization. [17] Similar to MoS 2 , the synthesis of tungsten disulfide (WS 2 ) nanorods has been accomplished by lengthy hydrothermal [18,19] and sulfidation [20] methods. Zhang et al. used high energy ball milling of WS 2 powder for 122 h, after which the powder was used as a precursor in a hydrothermal reaction for nanorod growth. [21] Ball milling methods have also been used to produce boron nitride (BN) nanorods. Boron carbide powders were milled for 100 h and subsequently treated with nitrogen at high temperature to produce BN nanorods. [22][23][24] In another approach, Museur et al. synthesized BN nanorods embedded in amorphous boron suboxides (B x O y ) through UV laser irradiation of a compacted BN powder pellet in a high-pressure nitrogen environment. [25] Table 1 summarizes these previous efforts to fabricate nanorods of 2D materials. Many of these methods require Herein, the previously unrealized ability to grow nanorods and nanotubes of 2D materials using femtosecond laser irradiation is demonstrated. In as short as 20 min, nanorods of tungsten disulfide, molybdenum disulfide, graphene, and boron nitride are grown in solutions. The technique fragments nanoparticles of the 2D materials from bulk flakes and leverages molecular scale alignment by nonresonant intense laser pulses to direct their assembly into nanorods up to several micrometers i...

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Section: Resultssupporting

confidence: 92%

Laser‐Directed Assembly of Nanorods of 2D Materials

Ibrahim

Novodchuk

Mistry

et al. 2019

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“…The curvature strain shifts the calculated spectra of optical absorption toward lower energies in unrelaxed MoS 2 NTs, whereas the strain relaxation leads to the shift of absorption peaks toward higher energies . The concept of the strain influence on optical properties was later developed in a set of papers . The DFT calculations showed that the properties similar to those in the monolayer and bulk are realized, respectively, in a large diameter single‐wall NT and a multiwalled NT.…”

Section: Basic Optical Properties Of Tmd Nanotubes and Related Curvedmentioning

confidence: 99%

Excitonic Emission in van der Waals Nanotubes of Transition Metal Dichalcogenides

et al. 2019

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Nanotubes (NTs) of transition metal dichalcogenides (TMDs), were first synthesized more than a quarter of a century ago; nevertheless, many of their optical properties have so far remained basically unknown. Herein, the state of the art in the knowledge of the optical properties of TMD NTs is presented. First, general properties of multilayered crystals are evaluated, and available data on related NTs are analyzed. Then, the technology for the formation and the structural characteristics of NTs are represented, focusing on the structures synthesized by chemical transport reaction. The core of this work is the presentation of the ability of synthesized TMD NTs to emit bright photoluminescence (PL), which has been discovered recently. By means of micro-PL spectroscopy of individual tubes, we show that excitonic transitions relevant to both direct and indirect band gaps contribute to the emission spectra of the NTs despite having the dozens of monolayers in their walls. The performance of the tubes as efficient optical resonators is highlighted, where confined optical modes strongly affect the emission. Finally, a brief conclusion is presented, along with an outlook of the future studies of this novel radiative member of the NTs family, which have unique potential for different nanophotonics applications.

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“…Where the last term result from strain ( () T  ) due to TEC mismatch. It is given as [29]. First term in eq n .…”

Section: Thermal Expansion Coefficientmentioning

confidence: 99%

Thermal expansion coefficient and phonon dynamics in coexisting allotropes of monolayer WS₂ probed by Raman scattering

Kumar

Singh

Kumar

et al. 2019

J. Phys.: Condens. Matter

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We report a comprehensive temperature dependent Raman measurements on three different phases of monolayer WS2 from 4K to 330K in a wide spectral range. Our studies revels the anomalous nature of the first as well as the higher order combination modes reflected in the disappearance of the few modes and anomalous temperature evaluation of the phonon self-energy parameters attributed to the detuning of resonance condition and development of strain due to thermal expansion mismatch with the underlying substrate. Our detailed temperature dependence studies also decipher the ambiguity about assignment of the two modes in literature near ~ 297 cm -1 and 325 cm -1 . Mode near 297 cm -1 is assigned as 1g E first order Raman mode, which is forbidden in the backscattering geometry and 325 cm -1 is assigned to the combination of 2 2 g E and LA mode. We also estimated thermal expansion coefficient by systematically disentangling the substrate effect in the temperature range of 4K to 330K and probed its temperature dependence in 1H, 1T and 1T' phases.#

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Strain-induced phonon shifts in tungsten disulfide nanoplatelets and nanotubes

Cited by 104 publications

References 76 publications

Laser‐Directed Assembly of Nanorods of 2D Materials

Laser‐Directed Assembly of Nanorods of 2D Materials

Excitonic Emission in van der Waals Nanotubes of Transition Metal Dichalcogenides

Thermal expansion coefficient and phonon dynamics in coexisting allotropes of monolayer WS₂ probed by Raman scattering

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Strain-induced phonon shifts in tungsten disulfide nanoplatelets and nanotubes

Cited by 104 publications

References 76 publications

Laser‐Directed Assembly of Nanorods of 2D Materials

Laser‐Directed Assembly of Nanorods of 2D Materials

Excitonic Emission in van der Waals Nanotubes of Transition Metal Dichalcogenides

Thermal expansion coefficient and phonon dynamics in coexisting allotropes of monolayer WS2 probed by Raman scattering

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Thermal expansion coefficient and phonon dynamics in coexisting allotropes of monolayer WS₂ probed by Raman scattering