Layer number identification of intrinsic and defective multilayered graphenes up to 100 layers by the Raman mode intensity from substrates

Li, Xiaoli; Qiao, Xiaoqiang; Han, Wenjuan; Lü, Yan; Tan, Qinghai; Liu, Xue-Lu; Tan, Ping‐Heng

doi:10.1039/c5nr01514f

Cited by 76 publications

(124 citation statements)

References 30 publications

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“…1(b), the minimum height between sample and substrate is about 4.7 nm. This is reasonable in consideration of the instrumental offset between the samples and substrate [13,27,28]. The typical PL spectra of 1L and 3L MoTe 2 on 300-nm SiO 2 /Si substrate are shown can be treated as a ball to analyze the atomic displacements of the interlayer modes, i.e., the socalled linear chain model (LCM) [13,18,25,29].…”

Section: Resultsmentioning

confidence: 99%

Physical origin of Davydov splitting and resonant Raman spectroscopy of Davydov components in multilayerMoTe2

et al. 2016

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We systematically study the high-resolution and polarized Raman spectra of multilayer (ML) Our work also provides a direct evidence from Raman spectroscopy of how the nearest van der Waals interactions significantly affect the frequency of the high-frequency intralayer phonon modes in multilayer MoTe 2 and expands the understanding on the lattice vibrations and interlayer coupling of transition metal dichalcogenides and other two-dimensional materials.

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Section: Resultsmentioning

confidence: 99%

Physical origin of Davydov splitting and resonant Raman spectroscopy of Davydov components in multilayerMoTe2

et al. 2016

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“…44 For most of the Raman modes, thick samples have red-shifted peak positions compared to thinner samples. A detailed discussion of layer-number dependence of high frequency Raman modes is included in the discussions section.…”

Section: Experiments and Resultsmentioning

confidence: 99%

Interlayer interactions in anisotropic atomically thin rhenium diselenide

et al. 2015

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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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“…However, the alloy flakes with the same layer number exhibit the C modes with almost the same frequency, in spite of the significant peak intensity due to the optical interference effect in the MoWS 2 /SiO 2 /Si multilayer. 13,16 Alloy flakes with different layer number display disparate C modes, offering a reliable diagnostic of the layer number. Similar behavior has also been observed for the LB modes (not shown here).…”

mentioning

confidence: 99%

“…[10][11][12][13][14][15][16] Nevertheless, most techniques rely on the specific properties of 2D materials. For example, one can identify the layer number, denoted as N, of MoS 2 by the intensity or peak positions of the corresponding photoluminescence (PL) peak and Raman modes.…”

mentioning

confidence: 99%

Substrate-free layer-number identification of two-dimensional materials: A case of Mo0.5W0.5S2 alloy

Qiao

Zhang

et al. 2015

Applied Physics Letters

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Any of two or more two-dimensional (2D) materials with similar properties can be alloyed into a new layered material, namely, 2D alloy. Individual monolayer in 2D alloys are kept together by Van der Waals interactions. The property of multilayer alloys is a function of their layer number. Here, we studied the shear (C) and layerbreathing (LB) modes of Mo 0.5 W 0.5 S 2 alloy flakes and their link to the layer number of alloy flakes. The study reveals that the disorder effect is absent in the C and LB modes of 2D alloys, and the monatomic chain model can be used to estimate the frequencies of the C and LB modes. We demonstrated how to use the C and LB mode frequency to identify the layer number of alloy flakes deposited on different substrates. This technique is independent of the substrate, stoichiometry, monolayer thickness and complex refractive index of 2D materials, offering a robust and substrate-free approach for layer-number identification of 2D materials. [6][7][8][9] The 2D alloys are a rich source of 2D materials because they can exhibit tunable properties because the ratio of two end compositions can be controllable. 6,9 The key to form a good quality of 2D monolayer is mixing the end compositions at atomic scale. Individual monolayers in the 2D alloys are kept together by Van der Waals interations. Similar to graphite and graphene, the property of multilayer alloys is a function of their layer number. How to determine the layer number of ultrathin 2D alloys is thus of primary importance for fundamental science and applications.Several optical techniques have been developed to identify the layer number of 2D materials. [10][11][12][13][14][15][16] Nevertheless, most techniques rely on the specific properties of 2D materials. For example, one can identify the layer number, denoted as N, of MoS 2 by the intensity or peak positions of the corresponding photoluminescence (PL) peak and Raman modes. 14,15 The mostly used technique is based upon optical contrast of 2D materials against dielectric substrates, such as a Si substrate covered with a SiO 2 layers. 10,12 To precisely identify N of few-layer 2D materials, the experimental optical contrast must be compared with the theoretical one for different N. However, the theoretical calculations require predetermined parameters, including thickness of a single layer, complex refractive index of the material and information of the substrate, 11,17 which poses great challenge for research on new 2D materials in early stage. Therefore, it is desirable to develop a novel approach to identify the layer number of fewlayer 2D materials, relying on as little prerequisite parameters as possible.The interlayer modes of multilayer 2D materials originates from the relative motions of the rigid monolayer planes themselves, either perpendicular or parallel to their normal, such as the shear (C) modes and the layer breathing (LB) modes. [18][19][20][21][22][23][24] The C and LB modes are the collective vibration modes of all the layers so their frequency (ω C and ω LB ) depe...

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Layer number identification of intrinsic and defective multilayered graphenes up to 100 layers by the Raman mode intensity from substrates

Cited by 76 publications

References 30 publications

Physical origin of Davydov splitting and resonant Raman spectroscopy of Davydov components in multilayerMoTe2

Physical origin of Davydov splitting and resonant Raman spectroscopy of Davydov components in multilayerMoTe2

Interlayer interactions in anisotropic atomically thin rhenium diselenide

Substrate-free layer-number identification of two-dimensional materials: A case of Mo0.5W0.5S2 alloy

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