scholarly journals Engineering phonon polaritons in van der Waals heterostructures to enhance in-plane optical anisotropy

2019 ◽  
Vol 5 (4) ◽  
pp. eaau7171 ◽  
Author(s):  
Kundan Chaudhary ◽  
Michele Tamagnone ◽  
Mehdi Rezaee ◽  
D. Kwabena Bediako ◽  
Antonio Ambrosio ◽  
...  
Keyword(s):  
Optical Anisotropy ◽  
Hexagonal Boron Nitride ◽  
Near Field ◽  
Van Der Waals ◽  
Microscopy Study ◽  
Refractive Indices ◽  
Optical And Electrical Properties ◽  
Nanophotonic Devices ◽  
Two Dimensional Materials ◽  
Phonon Polaritons

Van der Waals (vdW) heterostructures assembled from layers of two-dimensional materials have attracted considerable interest due to their novel optical and electrical properties. Here, we report a scattering-type scanning near-field optical microscopy study of hexagonal boron nitride on black phosphorus (h-BN/BP) heterostructures, demonstrating the first direct observation of in-plane anisotropic phonon polariton modes in vdW heterostructures. Notably, the measured in-plane optical anisotropy along the armchair and zigzag crystal axes exceeds the ratio of refractive indices of BP in the x-y plane. We explain that this enhancement is due to the high confinement of the phonon polaritons in h-BN. We observe a maximum in-plane optical anisotropy of αmax = 1.25 in the frequency spectrum at 1405 to 1440 cm−1. These results provide new insights into the behavior of polaritons in vdW heterostructures, and the observed anisotropy enhancement paves the way to novel nanophotonic devices and to a new way to characterize optical anisotropy in thin films.

scholarly journals Extracting the Infrared Permittivity of SiO2 Substrates Locally by Near-Field Imaging of Phonon Polaritons in a van der Waals Crystal

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 120
Author(s):  
Patricia Aguilar-Merino ◽  
Gonzalo Álvarez-Pérez ◽  
Javier Taboada-Gutiérrez ◽  
Jiahua Duan ◽  
Iván Prieto ◽  
...  
Keyword(s):  
Molybdenum Trioxide ◽  
Hexagonal Boron Nitride ◽  
Near Field ◽  
Van Der Waals ◽  
Field Studies ◽  
Dielectric Substrates ◽  
Nanophotonic Devices ◽  
Near Field Imaging ◽  
Materials Research ◽  
Phonon Polaritons

Layered materials in which individual atomic layers are bonded by weak van der Waals forces (vdW materials) constitute one of the most prominent platforms for materials research. Particularly, polar vdW crystals, such as hexagonal boron nitride (h-BN), alpha-molybdenum trioxide (α-MoO3) or alpha-vanadium pentoxide (α-V2O5), have received significant attention in nano-optics, since they support phonon polaritons (PhPs)―light coupled to lattice vibrations― with strong electromagnetic confinement and low optical losses. Recently, correlative far- and near-field studies of α-MoO3 have been demonstrated as an effective strategy to accurately extract the permittivity of this material. Here, we use this accurately characterized and low-loss polaritonic material to sense its local dielectric environment, namely silica (SiO2), one of the most widespread substrates in nanotechnology. By studying the propagation of PhPs on α-MoO3 flakes with different thicknesses laying on SiO2 substrates via near-field microscopy (s-SNOM), we extract locally the infrared permittivity of SiO2. Our work reveals PhPs nanoimaging as a versatile method for the quantitative characterization of the local optical properties of dielectric substrates, crucial for understanding and predicting the response of nanomaterials and for the future scalability of integrated nanophotonic devices.

High-efficiency modulation of coupling between different polaritons in an in-plane graphene/hexagonal boron nitride heterostructure

Nanoscale ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 2703-2709 ◽  
Author(s):  
Xiangdong Guo ◽  
Hai Hu ◽  
Debo Hu ◽  
Baoxin Liao ◽  
Ke Chen ◽  
...  
Keyword(s):  
Boron Nitride ◽  
High Efficiency ◽  
Hexagonal Boron Nitride ◽  
Van Der Waals ◽  
Two Dimensional ◽  
Low Loss ◽  
Nanophotonic Devices ◽  
Phonon Polaritons ◽  
Graphene Plasmons

Two-dimensional van der Waals (vdW) materials have a full set of highly confined polariton modes, such as low-loss phonon polaritons and dynamically tunable graphene plasmons, which provide a solution for integrated nanophotonic devices by combining the unique advantages of different polaritons.

scholarly journals High-Q dark hyperbolic phonon-polaritons in hexagonal boron nitride nanostructures

Nanophotonics ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 1457-1467 ◽  
Author(s):  
Georg Ramer ◽  
Mohit Tuteja ◽  
Joseph R. Matson ◽  
Marcelo Davanco ◽  
Thomas G. Folland ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Cross Sections ◽  
Hexagonal Boron Nitride ◽  
Near Field ◽  
High Q ◽  
Surface Phonon Polaritons ◽  
Previous Hypothesis ◽  
Phonon Polaritons ◽  
Field Reflectance ◽  
Strong Confinement

AbstractThe anisotropy of hexagonal boron nitride (hBN) gives rise to hyperbolic phonon-polaritons (HPhPs), notable for their volumetric frequency-dependent propagation and strong confinement. For frustum (truncated nanocone) structures, theory predicts five, high-order HPhPs, sets, but only one set was observed previously with far-field reflectance and scattering-type scanning near-field optical microscopy. In contrast, the photothermal induced resonance (PTIR) technique has recently permitted sampling of the full HPhP dispersion and observing such elusive predicted modes; however, the mechanism underlying PTIR sensitivity to these weakly-scattering modes, while critical to their understanding, has not yet been clarified. Here, by comparing conventional contact- and newly developed tapping-mode PTIR, we show that the PTIR sensitivity to those weakly-scattering, high-Q (up to ≈280) modes is, contrary to a previous hypothesis, unrelated to the probe operation (contact or tapping) and is instead linked to PTIR ability to detect tip-launched dark, volumetrically-confined polaritons, rather than nanostructure-launched HPhPs modes observed by other techniques. Furthermore, we show that in contrast with plasmons and surface phonon-polaritons, whose Q-factors and optical cross-sections are typically degraded by the proximity of other nanostructures, the high-Q HPhP resonances are preserved even in high-density hBN frustum arrays, which is useful in sensing and quantum emission applications.

Photon Tunneling via Coupling Graphene Plasmons With Phonon Polaritons of Hexagonal Boron Nitride in Reststrahlen Bands

2021 ◽  
Author(s):  
Ruiyi Liu ◽  
Xiaohu Wu ◽  
Zheng Cui
Keyword(s):  
Boron Nitride ◽  
Chemical Potential ◽  
Hexagonal Boron Nitride ◽  
Near Field ◽  
Tunneling Probability ◽  
Coupling Mechanism ◽  
Work Study ◽  
Photon Tunneling ◽  
Phonon Polaritons ◽  
Graphene Plasmons

Abstract The photon tunneling probability is the most important thing in near-field radiative heat transfer (NFRHT). This work study the photon tunneling via coupling graphene plasmons with phonon polaritons in hexagonal boron nitride (hBN). We consider two cases of the optical axis of hBN along z-axis and x-axis, respectively. We investigate the NFRHT between graphene-covered bulk hBN, and compare it with that of bare bulk hBN. Our results show that in Reststrahlen bands, the coupling of graphene plasmons and phonon polaritons in hBN can either suppress or enhance the photon tunneling probability, depending on the chemical potential of graphene and frequency. This conclusion holds when the optiacal axis of hBN is either along z-axis or x-axis. The findings in this work not only deepen our understanding of coupling mechanism between graphene plasmons with phonon polaritons, but also provide a theoretical basis for controlling photon tunneling in graphene covered hyperbolic materials.

scholarly journals Making van der Waals Heterostructures Assembly Accessible to Everyone

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2305
Author(s):  
Sergey G. Martanov ◽  
Natalia K. Zhurbina ◽  
Mikhail V. Pugachev ◽  
Aliaksandr I. Duleba ◽  
Mark A. Akmaev ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Hexagonal Boron Nitride ◽  
Condensed Matter ◽  
Van Der Waals ◽  
Atomic Layer ◽  
Two Dimensional ◽  
Van Der Waals Heterostructures ◽  
Online Retail ◽  
Two Dimensional Materials ◽  
Retail Services

Van-der Waals heterostructures assembled from one or few atomic layer thickness crystals are becoming increasingly more popular in condensed matter physics. These structures are assembled using transfer machines, those are based on mask aligners, probe stations or are home-made. For many laboratories it is vital to build a simple, convenient and universal transfer machine. In this paper we discuss the guiding principles for the design of such a machine, review the existing machines and demonstrate our own construction, that is powerful and fast-in-operation. All components of this machine are extremely cheap and can be easily purchased using common online retail services. Moreover, assembling a heterostructure out of exfoliated commercially available hexagonal boron nitride and tungsten diselenide crystals with a pick-up technique and using the microphotolumenescence spectra, we show well-resolved exciton and trion lines, as a results of disorder suppression in WSe2 monolayer. Our results thus show that technology of the two-dimensional materials and heterostructures becomes accessible to anyone.

Near-Field Radiative Heat Transfer Between Two α-MoO3 Biaxial Crystals

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Xiaohu Wu ◽  
Ceji Fu ◽  
Zhuomin M. Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Hexagonal Boron Nitride ◽  
Near Field ◽  
Radiative Heat Flux ◽  
Relative Rotation ◽  
Maximum Heat ◽  
Phonon Polaritons

Abstract The near-field radiative heat transfer (NFRHT) between two semi-infinite α-MoO3 biaxial crystals is investigated numerically based on the fluctuation–dissipation theorem combined with the modified 4 × 4 transfer matrix method in this paper. In the calculations, the near-field radiative heat flux (NFRHF) along each of the crystalline directions of α-MoO3 is obtained by controlling the orientation of the biaxial crystals. The results show that much larger heat flux than that between two semi-infinite hexagonal boron nitride can be achieved in the near-field regime, and the maximum heat flux is along the [001] crystalline direction. The mechanisms for the large radiative heat flux are explained as due to existence of hyperbolic phonon polaritons (HPPs) inside α-MoO3 and excitation of hyperbolic surface phonon polaritons (HSPhPs) at the vacuum/α-MoO3 interfaces. The effect of relative rotation between the emitter and the receiver on the heat flux is also investigated. It is found that the heat flux varies significantly with the relative rotation angle. The modulation contrast can be as large as two when the heat flux is along the [010] direction. We attribute the large modulation contrast mainly to the misalignment of HSPhPs and HPPs between the emitter and the receiver. Hence, the results obtained in this work may provide a promising way for manipulating near-field radiative heat transfer between anisotropic materials.

Far-Field Spectroscopy and Near-Field Optical Imaging of Coupled Plasmon-Phonon Polaritons in 2D van der Waals Heterostructures

2016 ◽  
Vol 28 (15) ◽  
pp. 2931-2938 ◽  
Author(s):  
Xiaoxia Yang ◽  
Feng Zhai ◽  
Hai Hu ◽  
Debo Hu ◽  
Ruina Liu ◽  
...  
Keyword(s):  
Optical Imaging ◽  
Near Field ◽  
Van Der Waals ◽  
Far Field ◽  
Van Der Waals Heterostructures ◽  
Field Spectroscopy ◽  
Phonon Polaritons

scholarly journals Probing optical anisotropy of nanometer-thin van der waals microcrystals by near-field imaging

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Debo Hu ◽  
Xiaoxia Yang ◽  
Chi Li ◽  
Ruina Liu ◽  
Ziheng Yao ◽  
...  
Keyword(s):  
Optical Anisotropy ◽  
Near Field ◽  
Van Der Waals ◽  
Near Field Imaging ◽  
Field Imaging

scholarly journals Chlorosulfuric acid-assisted production of functional 2D materials

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Mohsen Moazzami Gudarzi ◽  
Maryana Asaad ◽  
Boyang Mao ◽  
Gergo Pinter ◽  
Jianqiang Guo ◽  
...  
Keyword(s):  
Hexagonal Boron Nitride ◽  
2D Materials ◽  
Real Life ◽  
Large Area ◽  
Polar Solvents ◽  
Aspect Ratios ◽  
Two Dimensional Materials ◽  
Liquid Phase Exfoliation

AbstractThe use of two-dimensional materials in bulk functional applications requires the ability to fabricate defect-free 2D sheets with large aspect ratios. Despite huge research efforts, current bulk exfoliation methods require a compromise between the quality of the final flakes and their lateral size, restricting the effectiveness of the product. In this work, we describe an intercalation-assisted exfoliation route, which allows the production of high-quality graphene, hexagonal boron nitride, and molybdenum disulfide 2D sheets with average aspect ratios 30 times larger than that obtained via conventional liquid-phase exfoliation. The combination of chlorosulfuric acid intercalation with in situ pyrene sulfonate functionalisation produces a suspension of thin large-area flakes, which are stable in various polar solvents. The described method is simple and requires no special laboratory conditions. We demonstrate that these suspensions can be used for fabrication of laminates and coatings with electrical properties suitable for a number of real-life applications.

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