Ultralow-frequency shear modes of 2-4 layer graphene observed in scroll structures at edges

Abstract. Recently, two-dimensional (2D) materials with strong in-plane anisotropic properties such as black phosphorus have demonstrated great potential for developing new devices that can take advantage of its reduced lattice symmetry with potential applications in electronics, optoelectronics and thermoelectrics. However, the selection of 2D material with strong in-plane anisotropy has so far been very limited and only sporadic studies have been devoted to transition metal dichalcogenides (TMDC) materials with reduced lattice symmetry, which is yet to convey the full picture of their optical and phonon properties, and the anisotropy in their interlayer interactions. Here, we study the anisotropic interlayer interactions in an important TMDC 2D material with reduced in-plane symmetry -atomically thin rhenium diselenide (ReSe2) -by investigating its ultralow frequency interlayer phonon vibration modes, the layernumber dependent optical bandgap, and the anisotropic photoluminescence (PL) spectra for the first time. The ultralow frequency interlayer Raman spectra combined with the first study of polarization-resolved high frequency Raman spectra in monoand bi-layer ReSe2 allows deterministic identification of its layer number and crystal orientation. PL measurements show anisotropic optical emission intensity with bandgap increasing from 1.26 eV in the bulk to 1.32 eV in monolayer, consistent with the theoretical results based on first-principle calculations. The study of the layer-number dependence of the Raman modes and the PL spectra reveals the relatively weak van der Waal's interaction and 2D quantum confinement in atomically-thin ReSe2. The experimental observation of the intriguing anisotropic interlayer interaction and tunable optical transition in mono-and multi-layer ReSe2 establishes the foundation for further exploration of this material to develop anisotropic optoelectronic devices in the nearinfrared spectrum range where many applications in optical communications and infrared sensing exist.

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“…[36][37][38][39][40][41][42] These modes only occur in multi-layers of ReSe2, but not in the monolayer samples. As shown in Fig.…”

Section: Experiments and Resultsmentioning

confidence: 99%

Interlayer interactions in anisotropic atomically thin rhenium diselenide

et al. 2015

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“…GNS can be single-layer or multilayer, the latter are produced by rolling up the multilayer graphene [53,54]. For such multilayer scrolls low-frequency vibrations were measured by Raman scattering [53]. GNS with a polygonal cross-section have been observed by high resolution transmission electron microscopy in films synthesized by chemical vapor deposition [30].…”

Section: Introductionmentioning

confidence: 99%

“…Well-defined CNSs can be formed by single-side hydrogenation and fluorination of graphene, according to the molecular dynamics simulations reported in [52]. GNS can be single-layer or multilayer, the latter are produced by rolling up the multilayer graphene [53,54]. For such multilayer scrolls low-frequency vibrations were measured by Raman scattering [53].…”

Section: Introductionmentioning

confidence: 99%

Graphene nanoribbon winding around carbon nanotube

Savin¹,

Korznikova

Soboleva

2017

Computational Materials Science

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“…This has significantly different properties when compared with a Bernal-stacked 5LG, or to a t (1 þ 4)LG, or t(1 þ 1 þ 3)LG and so on, even though all these have the same N ¼ 5. For a given total N, the choice of m, n and so on (with m þ n þ ... ¼ N) and relative angles between each m, n,...LGs leads to a family of systems with different optical and electronic properties 12,13 . The ability to probe the interlayer coupling between the interface layers of mLG and nLG in t(m þ n)LGs, and its impact on the electronic band structure and lattice dynamics, is crucial to reach a fundamental understanding of these systems and to tune them for novel applications.…”

mentioning

confidence: 99%

Resonant Raman spectroscopy of twisted multilayer graphene

et al. 2014

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Graphene and other two-dimensional crystals can be combined to form various hybrids and heterostructures, creating materials on demand with properties determined by the interlayer interaction. This is the case even for a single material, where multilayer stacks with different relative orientation have different optical and electronic properties. Probing and understanding the interface coupling is thus of primary importance for fundamental science and applications. Here we study twisted multilayer graphene flakes with multi-wavelength Raman spectroscopy. We find a significant intensity enhancement of the interlayer coupling modes (C peaks) due to resonance with new optically allowed electronic transitions, determined by the relative orientation of the layers. The interlayer coupling results in a Davydov splitting of the C peak in systems consisting of two equivalent graphene multilayers. This allows us to directly quantify the interlayer interaction, which is much smaller compared with Bernalstacked interfaces. This paves the way to the use of Raman spectroscopy to uncover the interface coupling of two-dimensional hybrids and heterostructures.

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Ultralow-frequency shear modes of 2-4 layer graphene observed in scroll structures at edges

Cited by 31 publications

References 55 publications

Interlayer interactions in anisotropic atomically thin rhenium diselenide

Interlayer interactions in anisotropic atomically thin rhenium diselenide

Graphene nanoribbon winding around carbon nanotube

Resonant Raman spectroscopy of twisted multilayer graphene

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