Resonant Raman and photoluminescence spectra of suspended molybdenum disulfide

Lee, Jae-Ung; Kim, Kangwon; Cheong, Hyeonsik

doi:10.1088/2053-1583/2/4/044003

Cited by 41 publications

(56 citation statements)

References 41 publications

(75 reference statements)

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“…The relative increase of the intensity of the A′ 1 /A 1g to the E′ / E g / E 1 2g can be attributed to increased out‐of‐plane motion of the sulfur atoms when free of substrate interactions. The red shift for both modes upon suspension of MoS 2 has previously been attributed to a release from residual substrate strain or doping . Previous reports have also suggested that this shift may be due to biaxial strain in MoS 2 as it “sags” over the holey area, and calculated a red‐shift rate of strain of −2.2 cm −1 /% for the A ′ 1 /A 1g mode and −5.2 cm −1 /% for the E′ / E g / E 1 2g mode in bilayer MoS 2 .…”

Section: Resultsmentioning

confidence: 80%

“…The red shift for both modes upon suspension of MoS 2 has previously been attributed to a release from residual substrate strain or doping. [24] Previous reports have also suggested that this shift may be due to biaxial strain in MoS 2 as it "sags" over the holey area, [25] and calculated a red-shift rate of strain of À2.2 cm À1 /% for the A 0 1 /A 1g mode and À5.2 cm À1 /% for the E 0 /E g /E 1 2g mode in bilayer MoS 2 . Using these values as benchmarks for this work results in an estimation of biaxial tensile strain for the suspended 2L MoS 2 presented here of $ 1.77% from the E 0 /E g /E 1 2g red-shift of $9.2 cm À1 , and $3.02% from the A 0 1 /A 1g red-shift of $6.7 cm À1 .…”

Section: Resultsmentioning

confidence: 89%

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Raman Spectroscopy of Suspended MoS₂

O’Brien

Scheuschner²,

Maultzsch

et al. 2017

Physica Status Solidi (b)

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This report details the Raman spectroscopic characterization of suspended MoS2. MoS2 was grown by chemical vapor deposition (CVD) and then transferred onto holey substrates using a polymer‐assisted technique, allowing measurement of suspended MoS2. Significant differences in the spectral characteristics of suspended and supported MoS2 were observed which are attributed to strain in the MoS2 suspended over the holey regions of the substrate. In particular, we investigate the low‐frequency Raman spectrum of free‐standing CVD‐grown MoS2, and estimate the strain caused in the layers by suspension over holes.

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Section: Resultsmentioning

confidence: 80%

Section: Resultsmentioning

confidence: 89%

Raman Spectroscopy of Suspended MoS₂

O’Brien

Scheuschner²,

Maultzsch

et al. 2017

Physica Status Solidi (b)

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“…The breathing modes are almost invisible except for the highest excitation energies, which is similar to the case of MoS2. 12,47 Since inter-layer vibrations are dominated by chalcogen to chalcogen interactions, no enhancement of shear and breathing modes at the A exciton state For resonance studies, normalization was carried out to extract the intrinsic resonance effects. First, the Raman intensities are normalized by the intensity of the Si Raman peak at 520 cm -1 for each excitation energy to correct for the efficiency of the detection system.…”

Section: Resultsmentioning

confidence: 99%

Davydov Splitting and Excitonic Resonance Effects in Raman Spectra of Few-Layer MoSe₂

et al. 2016

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Raman spectra of few-layer MoSe2 were measured with 8 excitation energies. New peaks that appear only near resonance with various exciton states are analyzed, and the modes are assigned.The resonance profiles of the Raman peaks reflect the joint density of states for optical transitions, but the symmetry of the exciton wave functions leads to selective enhancement of the A1g mode at the A exciton energy and the shear mode at the C exciton energy. We also find Davydov splitting of intra-layer A1g, E1g, and A2u modes due to inter-layer interaction for some excitation energies near resonances. Furthermore, by fitting the spectral positions of inter-layer shear and breathing modes and Davydov splitting of intra-layer modes to a linear chain model, we extract the strength of the inter-layer interaction. We find that the second-nearest-neighbor inter-layer interaction amounts to about 30% of the nearest-neighbor interaction for both in-plane and out-of-plane vibrations. 2 KEYWORDSMoSe2, Molybdenum diselenide, Raman spectroscopy, Davydov splitting, excitonic resonance 3 Few-layer semiconducting transition metal dichalcogenides (TMD's) are studied intensively owing to bandgap energies in the range of near infrared to visible wavelengths which make them suitable for various electronic and optoelectronic applications. 1,2 Monolayer MoSe2 shows a luminescence peak at ~1.6 eV which is suitable for applications in deep red or near infrared regions of the spectrum. MoSe2 is also used in TMD heterostructures such as WSe2/MoSe2 3,4 or MoS2/MoSe2 5,6 which exhibit interesting physical properties due to unique band alignment between these atomically thin semiconductors. Raman spectroscopy is a powerful tool to characterize 2-dimensional materials such as graphene or TMD's. For TMD materials, Raman spectroscopy is used to characterize the number of layers, 7-9 the stacking order, 10-12 strain, 13,14 or doping density. 15 However, it has been reported that the Raman spectrum of a TMD material varies greatly depending on the excitation laser used, which is attributed to excitonic resonance effects. [16][17][18][19] Because of reduced dielectric screening in 2-dimensional materials, the excitons in TMD's are known to have very large binding energies, [20][21][22][23][24] and so tightly localized wave functions. Resonance with such exciton states greatly modifies the Raman scattering process to result in extraordinary resonance Raman effects. In the Raman spectra of MoTe2 and WS2, Davydov splitting of some of the main Raman peaks have been reported. [25][26][27] Davydov splitting, also known as factor-group splitting, is the splitting of bands in the electronic or vibrational spectra of crystals due to the presence of more than one equivalent entity in the unit cell. 28,29 Since this is due to breaking of degeneracy by interactions of each entity, it is an important probe to investigate interactions between each system. In TMD's, the weak inter-layer interaction causes splitting of the intra-layer vibration modes. Since this s...

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“…The performance of devices based on 2D heterostructures can also be improved by optimizing light absorption in the stack by coupling plasmonic nanoantennae or microcavities to the structures [14][15][16]. In 2D materials, there is another convenient way to enhance light coupling by modifying the layer structure and the dielectric surroundings of the device with a suitable substrate [17][18][19][20][21][22].…”

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confidence: 99%

Optimal light harvesting in 2D semiconductor heterostructures

2017

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Optoelectronics with two dimensional (2D) heterostructures combining transition metal dichalcogenides (TMDCs) and other semiconductors in hybrid stacks is potentially promising because of the possibility of fabricating devices with high efficiency and new properties. Ultrafast charge transfer across the interface and long lifetime of carriers makes the vertical geometry attractive with respect to traditional bulk heterostructures. In such ultrathin structures, the multiple boundaries and the thickness of each material play a key role in the interaction of light with the device and can strongly influence the device performance. In this article we study light harvesting in 2D InSe/MoS 2 semiconductor heterostructures by measuring Raman enhancement or attenuation as a function of layer thicknesses. Measurements are precisely reproduced by the calculation of the light emission, and the field distribution inside the heterostructure. Optimizing layer thickness and material interfaces has a significant effect on the light distribution in such 2D heterostructures with layer thickness in the region of a few tens of nanometers, providing a means to enhance the performance of emerging 2D semiconductor-heterostructure optoelectronics.

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Resonant Raman and photoluminescence spectra of suspended molybdenum disulfide

Cited by 41 publications

References 41 publications

Raman Spectroscopy of Suspended MoS₂

Raman Spectroscopy of Suspended MoS₂

Davydov Splitting and Excitonic Resonance Effects in Raman Spectra of Few-Layer MoSe₂

Optimal light harvesting in 2D semiconductor heterostructures

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Resonant Raman and photoluminescence spectra of suspended molybdenum disulfide

Cited by 41 publications

References 41 publications

Raman Spectroscopy of Suspended MoS2

Raman Spectroscopy of Suspended MoS2

Davydov Splitting and Excitonic Resonance Effects in Raman Spectra of Few-Layer MoSe2

Optimal light harvesting in 2D semiconductor heterostructures

Contact Info

Product

Resources

About

Raman Spectroscopy of Suspended MoS₂

Raman Spectroscopy of Suspended MoS₂

Davydov Splitting and Excitonic Resonance Effects in Raman Spectra of Few-Layer MoSe₂