High-<i>Q</i> Phonon-polaritons in Spatially Confined Freestanding α-MoO<sub>3</sub>

Yang, Jiong; Tang, Jianbo; Ghasemian, Mohammad B.; Mayyas, Mohannad; Yu, Qiuhui V.; Li, Lu Hua; Kalantar‐zadeh, Kourosh

doi:10.1021/acsphotonics.1c01726

Cited by 19 publications

(33 citation statements)

References 37 publications

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“…An intriguing feature of phonon polaritons is the possibility of anisotropic propagation due to the complex crystal structure of polar dielectrics, related to the simultaneous presence (i.e., at fixed frequency) of both positive and negative terms in the dielectric tensor. − Thin films of layered van der Waals (vdW) materials have attracted considerable attention as they support highly anisotropic hyperbolic and elliptical phonon polaritons, combined with extreme subdiffractional confinement. − More recently, the possibility of twisting one layer with respect to the other has increased the dispersion engineering possibilities in these novel vdW materials. − …”

Section: Introductionmentioning

confidence: 99%

Near-Field Retrieval of the Surface Phonon Polariton Dispersion in Free-Standing Silicon Carbide Thin Films

et al. 2022

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Surface phonon polaritons (SPhPs) are mixed light-matter states originating from strong coupling of photons with lattice vibrations. Thin films of polar dielectrics feature a splitting of the SPhP branch due to the hybridization of the top and bottom interface modes. Recently, enhanced in-plane thermal conductivity and near-field energy transfer have been experimentally demonstrated in free-standing polar films. These effects are determined by the SPhP dispersion in these systems, which, however, is yet to be reported experimentally. In this work, we retrieve the SPhP dispersion in silicon carbide free-standing membranes few hundreds of nanometers thick through near-field spectroscopy. We find several branches in the experimental dispersion, which we rationalize as multiple reflections of tip and edge launched SPhPs, in good agreement with theoretical predictions. Our work paves the way to employ large-area free-standing membranes as a platform for phonon polaritonics, with foreseeable applications in the field of thermal management at the nanoscale.

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Section: Introductionmentioning

confidence: 99%

Near-Field Retrieval of the Surface Phonon Polariton Dispersion in Free-Standing Silicon Carbide Thin Films

et al. 2022

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“…In this context, the development of MoO 3 nanoparticles has attracted a great deal of attention due to their unique properties and consequently their study increased in recent years, while playing a critical role in many applications [19–21] . Various MoO 3 nanostructures in the α‐phase, were synthesized by different methods, being the hydrothermal method the most used.…”

Section: Introductionmentioning

confidence: 99%

“…[15][16][17][18] In this context, the development of MoO 3 nanoparticles has attracted a great deal of attention due to their unique properties and consequently their study increased in recent years, while playing a critical role in many applications. [19][20][21] Various MoO 3 nanostructures in the α-phase, were synthesized by different methods, being the hydrothermal method the most used. The hydrothermal method is simple and cost effective, as it is a low temperature process, which yields various nanostructures with controlled size, stoichiometry and shape.…”

Section: Introductionmentioning

confidence: 99%

Oxidative Desulfurization Using MoO₃ as Recyclable and Efficient Nanocatalyst

Sales

Nunes

2022

ChemCatChem

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Gathering clean energy from fuel feedstocks is of paramount significance in environmental science. In this area, desulfurization provides a valuable contribution by eliminating sulfur compounds from fuel feedstocks to ensure they can be used without emission of toxic sulfur oxides. MoO3 nanoparticles have been hydrothermally synthesized and used as efficient catalyst in the oxidative desulfurization (ODS) of methylphenyl and diphenyl sulfide using TBHP or H2O2 as oxidant. The catalyst showed an enhancement in the ODS process of the two substrates revealing influence on the reaction rate and product selectivity. Temperature and solvent influenced the conversion for the desired product as well. The activity of the catalyst was stable for at least 3 continuous catalytic cycles. Catalytic performance of MoO3 nanomaterial was comparable or better than other catalysts reported in the literature in terms of the sulfoxide or sulfone yield.

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“…Hyperbolic phonon‐polaritons (HPhPs), as recently demonstrated in van der Waals materials, is very promising for light control at nanoscale due to their inherent advantages including high confinement, negligible electronic loss, long propagating distance, and large tunable energy range. [ 1–4 ] Among the emerging natural hyperbolic materials, a particular interest has been focused on orthorhombic‐phase molybdenum trioxide (α‐MoO 3 ) for sustaining extremely anisotropic HPhPs in the mid‐IR range, which also provides multiple photonic operation routes such as the layer‐twisting, [ 5–8 ] heterojunction, [ 9 ] artificial structure, [ 10–15 ] doping, [ 16,17 ] and ambient dielectric modulation. [ 11,18,19 ] These highly anisotropic HPhPs of α‐MoO 3 stem from three so‐called Reststrahlen bands (RBs) with opposite‐signed refractive indices along the three principal crystal orientations in the mid‐IR range, which results from the strong anisotropic structure.…”

Section: Introductionmentioning

confidence: 99%

In‐Plane Hyperbolic Phonon‐Polaritons in van der Waals Nanocrystals

Huang

Lei

Dong

et al. 2022

Advanced Optical Materials

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tunable energy range. [1][2][3][4] Among the emerging natural hyperbolic materials, a particular interest has been focused on orthorhombic-phase molybdenum trioxide (α-MoO 3 ) for sustaining extremely anisotropic HPhPs in the mid-IR range, which also provides multiple photonic operation routes such as the layer-twisting, [5][6][7][8] heterojunction, [9] artificial structure, [10][11][12][13][14][15] doping, [16,17] and ambient dielectric modulation. [11,18,19] These highly anisotropic HPhPs of α-MoO 3 stem from three socalled Reststrahlen bands (RBs) with opposite-signed refractive indices along the three principal crystal orientations in the mid-IR range, which results from the strong anisotropic structure. [2,3,20] The spectral energy in RB1 (545-850 cm −1 ) and RB2 (820-972 cm −1 ) supports in-plane hyperbolic polaritonic modes (along [001] and [100], respectively), while RB3 (958 to 1010 cm −1 ) sustains the in-plane elliptic polaritonic modes (Figure S1, Supporting Information). [3] To date, the investigations on the HPhP launching and propagating in α-MoO 3 have predominately been limited to photon wavenumbers in the range of 900-1010 cm −1 (9.9-11.1 µm) through scattering-type scanning near-field optical microscopy (s-SNOM), which covers RB3 and the upper part of RB2. Few spectral studies based on nano-FTIR have extended to the mid-IR transverse optical (TO) phonon frequency of RB2 (820 cm −1 ) using a broadband source, and the nano-imaging studies in this spectral range usually need to be reconstructed from the hyperspectral data. [2,10,21] Two possible reasons make it challenging to study HPhPs in this spectral band through s-SNOM. First, a polarized and high-power narrowband laser source in this mid-IR range (like the free-electron laser [22] ), or a broadband mid-IR radiation (like synchrotron source [21,23,24] ), is not readily accessible, which is essential to obtain a highquality near-field optical nano-image. [25][26][27][28] Second, the inherent damping rate of HPhPs in α-MoO 3 dramatically increases toward the TO phonon frequencies at 820 cm −1 (the lower band edge of RB2), which hinders the observation of HPhPs in this range. [1,3,12] Alternatively, Gao et al. employed an electron beam instead of a light source through electron energy loss spectroscopy (EELS) to investigate HPhPs in a large energy range that covers all three full RBs in mid-IR. [4] However, this nonoptical technique has a short penetration depth and a low spectral energy resolution limit. [4] The in-plane anisotropic HPhPs properties, especially in the spectral range that covers both RB1 Anisotropic hyperbolic phonon-polaritons (HPhPs) in a van der Waals material, orthorhombic-phase molybdenum trioxide (α-MoO 3 ), provide strategies in multiple dimensions to manipulate photons at the nanoscale. However, the nano-imaging studies of the in-plane HPhPs along orthogonal crystal orientations are still rare. In this work, the launching and propagating properties of HPhPs are studied in α-MoO 3 upon a holey silicon nitride microcavity ...

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High-Q Phonon-polaritons in Spatially Confined Freestanding α-MoO₃

Cited by 19 publications

References 37 publications

Near-Field Retrieval of the Surface Phonon Polariton Dispersion in Free-Standing Silicon Carbide Thin Films

Near-Field Retrieval of the Surface Phonon Polariton Dispersion in Free-Standing Silicon Carbide Thin Films

Oxidative Desulfurization Using MoO₃ as Recyclable and Efficient Nanocatalyst

In‐Plane Hyperbolic Phonon‐Polaritons in van der Waals Nanocrystals

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High-Q Phonon-polaritons in Spatially Confined Freestanding α-MoO3

Cited by 19 publications

References 37 publications

Near-Field Retrieval of the Surface Phonon Polariton Dispersion in Free-Standing Silicon Carbide Thin Films

Near-Field Retrieval of the Surface Phonon Polariton Dispersion in Free-Standing Silicon Carbide Thin Films

Oxidative Desulfurization Using MoO3 as Recyclable and Efficient Nanocatalyst

In‐Plane Hyperbolic Phonon‐Polaritons in van der Waals Nanocrystals

Contact Info

Product

Resources

About

High-Q Phonon-polaritons in Spatially Confined Freestanding α-MoO₃

Oxidative Desulfurization Using MoO₃ as Recyclable and Efficient Nanocatalyst