Low frequency Raman spectroscopy of few-atomic-layer thick hBN crystals

Stenger, Ingrid; Schue, Léonard; Boukhicha, Mohamed; Bérini, Bruno; Plaçais, Bernard; Loiseau, Annick; Barjon, Julien

doi:10.1088/2053-1583/aa77d4

Cited by 95 publications

(95 citation statements)

References 25 publications

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“…In figure 3(c), the out-of-plane vibrational mode for bulk MoSe2 is observed at 240 cm -1 , whereas the weaker in-plane vibration mode is found at 295 cm -1 31 . In the case of h-BN excited with a laser in the visible range, the Raman processes are nonresonant and consequently, Raman spectra are much weaker 34 . The number of layers for the two of the h-BN samples was estimated through AFM characterization by measuring the step height with respect to the SiO2/Si substrate and found to be 4 layers (~2nm) and 20 layers (~9nm).…”

Section: Sample Preparation and Materials Characterizationmentioning

confidence: 99%

Simultaneous measurement of anisotropic thermal conductivity and thermal boundary conductance of 2-dimensional materials

Rahman

Shahzadeh

Pisana

2019

Journal of Applied Physics

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The rapidly increasing number of 2-dimensional (2D) materials that have been isolated or synthesized provides an enormous opportunity to realize new device functionalities. Whereas their optical and electrical characterization have been more readily reported, quantitative thermal characterization is more challenging due to the difficulties with localizing heat flow. Optical pump-probe techniques that are well-established for the study of bulk materials or thinfilms have limited sensitivity to in-plane heat transport, and the characterization of the thermal anisotropy that is common in 2D materials is therefore challenging. Here we present a new approach to quantify the thermal properties based on the magneto-optical Kerr effect that yields quantitative insight into cross-plane and in-plane heat transport. The use of a very thin magnetic material as heater/thermometer increases in-plane thermal gradients without complicating the data analysis in spite of the layer being optically semi-transparent. The approach has the added benefit that it does not require the sample to be suspended, providing insight of thermal transport in supported, device-like environments. We apply this approach to measure the thermal properties of a range of 2D materials which are of interest for device applications, including single layer graphene, few-layer h-BN, single and few layer MoS2, and bulk MoSe2 crystal. The measured thermal properties will have important implications for thermal management in device applications.

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Section: Sample Preparation and Materials Characterizationmentioning

confidence: 99%

Simultaneous measurement of anisotropic thermal conductivity and thermal boundary conductance of 2-dimensional materials

Rahman

Shahzadeh

Pisana

2019

Journal of Applied Physics

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“…11 The temperature dependence of the E low 2g mode has been used to monitor laser heating in Raman experiments on few-layer h-BN samples. 12 Phonon studies on isotopic dependence are even more scarce. In a recent publication, 13 we analyzed the isotopic effects on the phonon anharmonic decay of the high-energy Ramanactive mode of h-BN.…”

Section: Introductionmentioning

confidence: 99%

Influence of isotopic substitution on the anharmonicity of the interlayer shear mode of h -BN

et al. 2019

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We present a detailed analysis of the temperature dependence of the interlayer shear mode that reveals a variation of the 4-phonon scattering coupling with isotopic mass. Phonon anharmonic decay and isotopic disorder effects are very weak for the low-energy interlayer shear mode, and the overall temperature dependence is mainly governed by the thermal lattice expansion. This allows us to observe systematic differences in the temperature dependence of the low energy mode with the isotopic mass that are related to the 4-phonon scattering contribution in quartic anharmonicity. The change in the quartic anharmonicity coefficient between the isotopically pure samples is larger than it would be purely expected from the mass variation.

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“…Naturally, the dimensionality of a system has profound impact on both phonons and excitons [38,[62][63][64]. To elaborate the influence of hBN thickness on interlayer EPC of WS 2 /hBN heterostructures, we covered a thin hBN with various thicknesses on monolayer WS 2 by a dry transfer method.…”

mentioning

confidence: 99%

Strong and tunable interlayer coupling of infrared-active phonons to excitons in van der Waals heterostructures

Zhao

Jia

et al. 2019

Phys. Rev. B

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Understanding and manipulating the quantum interlayer exciton-phonon coupling in van der Waals heterostructures, especially for infrared active phonons with electromagnetic fields, would set a foundation for realizing exotic quantum phenomena and optoelectronic applications. Here we report experimental observations of strong mutual interactions between infrared active phonons in hexagonal boron nitride (hBN) and excitons in WS 2. Our results underscore that the infrared active A 2u mode of hBN becomes Raman active with strong intensities in WS 2 /hBN heterostructures through resonant coupling to the B exciton of WS 2. Moreover, we demonstrate that the activated A 2u phonon of hBN can be tuned by the hBN thickness and harbors a striking anticorrelation intensity modulation, as compared with the optically silent B 1g mode. Our observation of the interlayer exciton-infrared active phonon interactions and their evolution with hBN thickness provide a firm basis for engineering the hyperbolic exciton-phonon polaritons, chiral phonons and fascinating nanophotonics based on van der Waals heterostructures.

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Low frequency Raman spectroscopy of few-atomic-layer thick hBN crystals

Cited by 95 publications

References 25 publications

Simultaneous measurement of anisotropic thermal conductivity and thermal boundary conductance of 2-dimensional materials

Simultaneous measurement of anisotropic thermal conductivity and thermal boundary conductance of 2-dimensional materials

Influence of isotopic substitution on the anharmonicity of the interlayer shear mode of h -BN

Strong and tunable interlayer coupling of infrared-active phonons to excitons in van der Waals heterostructures

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