Evolution of Raman spectra as a function of layer thickness in ultra-thin InSe films

Schwarcz, Robert; Kanehisa, M.; Jouanne, M.; Morhange, J. F.; Eddrief, M.

doi:10.1088/0953-8984/14/5/302

Cited by 14 publications

(6 citation statements)

References 29 publications

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“…Second‐order modes are also visible at RT and result from overtones of E 1 2g (402 cm −1 ) and A 2u (423 cm −1 ) . It is worth noting that the peak positions of all modes have no significant energy shift in the ex‐InSe sample as is the case for c‐InSe (Figure S5, Supporting Information), which is in agreement with previous experimental studies . Interestingly, no modes relating to other InSe‐based compounds are observed, confirming that the stoichiometry is preserved without the formation of other chemical species during the exfoliation process .…”

Section: Resultssupporting

confidence: 89%

Liquid‐Phase Exfoliated Indium–Selenide Flakes and Their Application in Hydrogen Evolution Reaction

Petroni

Lago

Bellani

et al. 2018

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107

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Single- and few-layered InSe flakes are produced by the liquid-phase exfoliation of β-InSe single crystals in 2-propanol, obtaining stable dispersions with a concentration as high as 0.11 g L . Ultracentrifugation is used to tune the morphology, i.e., the lateral size and thickness of the as-produced InSe flakes. It is demonstrated that the obtained InSe flakes have maximum lateral sizes ranging from 30 nm to a few micrometers, and thicknesses ranging from 1 to 20 nm, with a maximum population centered at ≈5 nm, corresponding to 4 Se-In-In-Se quaternary layers. It is also shown that no formation of further InSe-based compounds (such as In Se ) or oxides occurs during the exfoliation process. The potential of these exfoliated-InSe few-layer flakes as a catalyst for the hydrogen evolution reaction (HER) is tested in hybrid single-walled carbon nanotubes/InSe heterostructures. The dependence of the InSe flakes' morphologies, i.e., surface area and thickness, on the HER performances is highlighted, achieving the best efficiencies with small flakes offering predominant edge effects. The theoretical model unveils the origin of the catalytic efficiency of InSe flakes, and correlates the catalytic activity to the Se vacancies at the edge of the flakes.

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Section: Resultssupporting

confidence: 89%

Liquid‐Phase Exfoliated Indium–Selenide Flakes and Their Application in Hydrogen Evolution Reaction

Petroni

Lago

Bellani

et al. 2018

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107

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“…Using the estimated values of η 0 , we obtain G 0 ∼ 1.0 and 1.5 THz for InSe and hBN, respectively. These values are smaller than the zone edge phonon frequencies for propagation perpendicular to the layers, i.e., f = 1.2 and 2.4 THz for InSe [81] and hBN [75], respectively, but much higher than the maximum phonon frequency f ∼ 100 GHz measured in our experiments. Thus we conclude that our use of the continuous approximation with bulk elastic parameters and sound velocity of InSe and hBN is valid in our analysis of the phonon spectra.…”

Section: A Elastic Properties Of Inse and Hbncontrasting

confidence: 77%

Coherent acoustic phonons in van der Waals nanolayers and heterostructures

et al. 2018

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Terahertz (THz) and sub-THz coherent acoustic phonons have been successfully used as probes of various quantum systems. Since their wavelength is in the nanometer range, they can probe nanostructures buried below a surface with nanometer resolution and enable control of electrical and optical properties on a picosecond time scale. However, coherent acoustic phonons have not yet been widely used to study van der Waals (vdW) two-dimensional (2D) materials and heterostructures. This class of 2D systems features strong covalent bonding of atoms in the layer planes and weak van der Waals attraction between the layers. The dynamical properties of the interface between the layers or between a layer and its supporting substrate are often omitted as they are difficult to probe. On the other hand, these play a crucial role in interpreting experiments and/or designing new device structures. Here, we use picosecond ultrasonic techniques to investigate phonon transport in vdW InSe nanolayers and InSe/hBN heterostructures. Coherent acoustic phonons are generated and detected in these 2D systems and allow us to probe elastic parameters of different layers and their interfaces. In particular, our study of the elastic properties of the interface between vdW layers reveals a strong coupling over a wide range of frequencies up to 0.1 THz, offering prospects for high-frequency electronics and technologies that require control over the charge and phonon transport across an interface. In contrast, we reveal a weak coupling between the InSe nanolayers and sapphire substrates, relevant in thermoelectrics and sensing applications, which can require quasi-suspended layers.

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“…The inset of figure 3(a) shows the Raman shift versus layer thickness of the A 1 (LO+TO), A 1 (TO), and A 1 (LO) peaks of as-grown β-In 2 Se 3 . The A 1 (LO+TO) mode at ∼110 cm −1 does not depend on the layer thickness, although, the A 1 (TO), and A 1 (LO) phonon modes exhibit a small shift to lower wavenumbers with decreasing L. This could arise from the smaller vibration coherence length along the c-axis due to the weak van der Waals force along this direction [26].…”

Section: Resultsmentioning

confidence: 91%

Quantum confinement and photoresponsivity of β -In ₂ Se ₃ nanosheets grown by physical vapour transport

et al. 2016

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We demonstrate that β-In 2 Se 3 layers with thickness ranging from 2.8 to 100 nm can be grown on SiO 2 /Si, mica and graphite using a physical vapour transport method. The β-In 2 Se 3 layers are chemically stable at room temperature and exhibit a blue-shift of the photoluminescence emission when the layer thickness is reduced, due to strong quantum confinement of carriers by the physical boundaries of the material. The layers are characterised using Raman spectroscopy and x-ray diffraction from which we confirm lattice constants c = 28.31 ± 0.05 Å and a = 3.99 ± 0.02 Å. In addition, these layers show high photoresponsivity of up to ∼2 × 10 3 A W −1 at λ = 633 nm, with rise and decay times of τ r = 0.6 ms and τ d = 2.5 ms, respectively, confirming the potential of the as-grown layers for high sensitivity photodetectors.

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Evolution of Raman spectra as a function of layer thickness in ultra-thin InSe films

Cited by 14 publications

References 29 publications

Liquid‐Phase Exfoliated Indium–Selenide Flakes and Their Application in Hydrogen Evolution Reaction

Liquid‐Phase Exfoliated Indium–Selenide Flakes and Their Application in Hydrogen Evolution Reaction

Coherent acoustic phonons in van der Waals nanolayers and heterostructures

Quantum confinement and photoresponsivity of β -In ₂ Se ₃ nanosheets grown by physical vapour transport

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Evolution of Raman spectra as a function of layer thickness in ultra-thin InSe films

Cited by 14 publications

References 29 publications

Liquid‐Phase Exfoliated Indium–Selenide Flakes and Their Application in Hydrogen Evolution Reaction

Liquid‐Phase Exfoliated Indium–Selenide Flakes and Their Application in Hydrogen Evolution Reaction

Coherent acoustic phonons in van der Waals nanolayers and heterostructures

Quantum confinement and photoresponsivity of β -In 2 Se 3 nanosheets grown by physical vapour transport

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Product

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Quantum confinement and photoresponsivity of β -In ₂ Se ₃ nanosheets grown by physical vapour transport