Layer‐Number Dependent Optical Properties of 2D Materials and Their Application for Thickness Determination

Li, Xiaoli; Han, Wenjuan; Wu, Jiang-Bin; Qiao, Xiaoqiang; Zhang, Jun; Tan, Ping‐Heng

doi:10.1002/adfm.201604468

Cited by 205 publications

(198 citation statements)

References 144 publications

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“…5d), where the maximum absorption occurs when incident polarized light is long the a -axis. In the incident light polarization rotation method, since the scattered polarization is fixed, the photon emission process has no influence on the Raman intensity’s polarization dependence 28 . When the scattered light polarization is along the a -axis ( θ 0 = 0°), this transition dispersion coincides with the calculated polarization-dependence of the A g phonon mode’s intensity.…”

Section: Resultsmentioning

confidence: 99%

Anomalous in-plane anisotropic Raman response of monoclinic semimetal 1 T´-MoTe 2

Song

Wang

Pan

et al. 2017

Sci Rep

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The recently discovered two-dimensional (2D) semimetal 1 T´-MoTe2 exhibits colossal magnetoresistance and superconductivity, driving a strong research interest in the material’s quantum phenomena. Unlike the typical hexagonal structure found in many 2D materials, the 1 T´-MoTe2 lattice has strong in-plane anisotropy. A full understanding of the anisotropy is necessary for the fabrication of future devices which may exploit these quantum and topological properties, yet a detailed study of the material’s anisotropy is currently lacking. While angle resolved Raman spectroscopy has been used to study anisotropic 2D materials, such as black phosphorus, there has been no in-depth study of the Raman dependence of 1 T´-MoTe2 on different layer numbers and excitation energies. Here, our angle resolved Raman spectroscopy shows intricate Raman anisotropy dependences of 1 T´-MoTe2 on polarization, flake thickness (from single layer to bulk), photon, and phonon energies. Using a Paczek approximation, the anisotropic Raman response can be captured in a classical framework. Quantum mechanically, first-principle calculations and group theory reveal that the anisotropic electron-photon and electron-phonon interactions are nontrivial in the observed responses. This study is a crucial step to enable potential applications of 1 T´-MoTe2 in novel electronic and optoelectronic devices where the anisotropic properties might be utilized for increased functionality and performance.

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Section: Resultsmentioning

confidence: 99%

Anomalous in-plane anisotropic Raman response of monoclinic semimetal 1 T´-MoTe 2

Song

Wang

Pan

et al. 2017

Sci Rep

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“…A 2D crystal structure has been a popular yet energy efficient choice for a large number of binary, ternary, and multinary chalcogenides of transition metals as well as P‐block elements (e.g., groups 13–15) . These chalcogenides form the basis for the explosion of experimental and theoretical research in the recent decade into the layer‐number dependent optical, electrical properties, and potential applications of these 2D materials . While a 2D structure for P‐block elements besides graphite carbon is uncommon, black phosphorous (BP) has been an outstanding example, which adopts a GeS‐type structure .…”

Section: Introductionmentioning

confidence: 99%

Linear and Nonlinear Optical Properties of Few‐Layer Exfoliated SnSe Nanosheets

Xian

Cai

et al. 2019

Advanced Optical Materials

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multinary [11,12] chalcogenides of transition metals as well as P-block elements (e.g., groups 13-15). [13][14][15][16][17][18][19][20][21] These chalcogenides form the basis for the explosion of experimental and theoretical research in the recent decade into the layer-number dependent optical, electrical properties, and potential applications of these 2D materials. [22][23][24][25] While a 2D structure for P-block elements besides graphite carbon is uncommon, black phosphorous (BP) has been an outstanding example, which adopts a GeS-type structure. [16][17][18][19][20][21] The connection between BP and the monochalcogenide GeS is quite obvious: they are isoelectronic with ten valence electrons per pair of atoms. [26][27][28][29] The monochalcogenide of group IV elements (i.e., Ge, Sn) has also been known as four-six-enes. [30] The most important difference from phosphorene is that they do not possess inversion symmetry for monolayer (or stacks with odd layer numbers), thus making them important candidates for exploiting piezo/ferro-electronic response as well as valleypolarized optical properties. [29,[31][32][33][34] Recently, their strong relevance with phosphorene and the chalcogenide 2D materials has stimulated growing interest in exploration of the potential properties from valleytronics to optical nonlinearity. [28,[35][36][37][38] Similar to many transition metal dichalcogenides, they have been predicted to show indirect to direct bandgap crossover at the monolayer limit, [28,[39][40][41] which however still await experimental confirmation. On the other hand, their bulk counterparts have been known for unconventional superconductivity, [42] ultrahigh thermoelectric figure of merit, [43][44][45] and photovoltaic properties, [41,[46][47][48] to name a few. The interplay between structural two-dimensionality and these features deserves a thorough examination, which is hampered by the limited access of high quality samples. Up to present, sheets of GeSe (or SnSe) with thickness of around 100 nm as well as Ge(Sn)Se nanowires and nanoplates have been reported by vapor transport process and liquid phase growth, [49][50][51][52][53][54][55][56][57][58][59] while access to few-layer and monolayer samples with high crystallinity by a top-down approach remain quite limited.In the present work, SnSe nanosheets were synthesized by sonication assisted exfoliation in different organic solvents. High quality FL SnSe nanosheets and clear layer number dependent optical bandgap is found, which is corroborated by our density functional theory (DFT) calculations. In addition, we also characterized the nonlinear optical absorption of FL SnSe Monochalcogenides of group IV elements have been considered as phosphorene analogs due to their similar crystal and electronic structure. Here, few-layer SnSe nanosheets are synthesized by a sonication-assisted liquid phase exfoliation process and their linear and nonlinear optical properties are examined. The as-exfoliated few-layer (FL) SnSe demonstrates layer thickness from 2 to 10 nm a...

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“…We used ultra-low frequency Raman spectroscopy [7,8] (the ultra-low frequency Raman spectra of SL MoS 2 and SL ReS 2 flakes supported on SiO 2 /Si substrate and supported on quartz substrate are shown in Additional file 1: Figure S3.) and photoluminescence (PL) spectroscopy [8,9] (the PL spectra of SL MoS 2 and SL ReS 2 flakes supported on SiO 2 /Si substrate and supported on quartz substrate are shown in Additional file 1: Figure S4.) to accurately determine the SL MoS 2 and ReS 2 flakes.…”

Section: Methodsmentioning

confidence: 99%

The Polarization Properties of the Reflection Spectra of Single-Layer MoS2 and ReS2 on SiO2/Si and Quartz Substrates

et al. 2020

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MoS 2 and ReS 2 are typical transition metal chalcogenides with many excellent electrical and optical properties. Due to different lattice symmetries, ReS 2 offers one more dimension than MoS 2 to tune its physical properties. In this paper, we studied the polarized reflection spectra in single-layer MoS 2 and ReS 2 . The explicit difference identifies strong angle-dependent properties in single-layer ReS 2 distinct from single-layer MoS 2 . The results of samples on both SiO 2 /Si substrate and quartz substrate show single-layer ReS 2 is in-plane anisotropic and the change period of reflection intensity is estimated with the polarization angles.

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Layer‐Number Dependent Optical Properties of 2D Materials and Their Application for Thickness Determination

Cited by 205 publications

References 144 publications

Anomalous in-plane anisotropic Raman response of monoclinic semimetal 1 T´-MoTe 2

Anomalous in-plane anisotropic Raman response of monoclinic semimetal 1 T´-MoTe 2

Linear and Nonlinear Optical Properties of Few‐Layer Exfoliated SnSe Nanosheets

The Polarization Properties of the Reflection Spectra of Single-Layer MoS2 and ReS2 on SiO2/Si and Quartz Substrates

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