Indirect Bandgap Puddles in Monolayer MoS<sub>2</sub> by Substrate‐Induced Local Strain

Shin, Bong Gyu; Han, Gang; Yun, Seok Joon; Oh, Hye Min; Bae, Jung Jun; Song, Young Jae; Park, Chong-Yun; Lee, Young Hee

doi:10.1002/adma.201602626

Cited by 136 publications

(131 citation statements)

References 36 publications

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“…The MoS 2 value 0.1% is in good agreement with the additional strain found in Ref. 21 in the case of MoS 2 on SiO 2 . Since the subsequent optical band gap change is only in the order of 10 meV, such a dramatic shift in the A-peak position in MoS 2 is not expected.…”

supporting

confidence: 79%

Optical study of local strain related disordering in CVD-grown MoSe2 monolayers

Krustok

Raadik

Jaaniso

et al. 2016

Applied Physics Letters

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Krustok, J.; Raadik, T.; Jaaniso, R.; Kiisk, V.; Sildos, I.; Marandi, M.; Komsa, Hannu-Pekka; Li, B.; Zhang, X.; Gong, Y.; Ajayan, P. M. We present temperature dependent micro-photoluminescence and room temperature photoreflectance spectroscopy studies on aged MoSe 2 monolayers with high surface roughness. A 0 and B 0 exciton bands were detected at 1.512 eV and 1.72 eV, respectively, which are 50-70 meV lower than those commonly reported for high-quality samples. It is shown that the difference can be accounted for using a model of localized excitons for disordered MoSe 2 monolayers where the optical band gap energy fluctuations could be caused by random distribution of local tensile strain due to surface roughness. The density of localized exciton states is found to follow the Lorentzian shape, where the peak of this distribution is about 70 meV from the energy of delocalized states. Optical study of local strain related disordering in CVD-grown MoSe2 monolayersPublished by AIP Publishing.[http://dx

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supporting

confidence: 79%

Optical study of local strain related disordering in CVD-grown MoSe2 monolayers

Krustok

Raadik

Jaaniso

et al. 2016

Applied Physics Letters

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“…Moreover, the indirect band gap resonance was expected to be less luminescent than a direct process. Compared to the data presented here or ref., 32 our situation was quite different as the nanostructuring gave rise to a strong strain gradient and involved fewer processes, which increased the indirect gap response: 1) The consequences of the exciton funneling effect are not easily determined in this configuration and can favor indirect band gap processes. 2) Suspended MoS2 has a more intense photoluminescence signal than non-suspended and our suspended part was the stressed region.…”

Section: Resultsmentioning

confidence: 94%

Intrinsic Properties of Suspended MoS₂ on SiO₂/Si Pillar Arrays for Nanomechanics and Optics

et al. 2018

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Semiconducting two-dimensional (2D) materials, such as transition-metal dichalcogenides (TMDs), are emerging in nanomechanics, optoelectronics, and thermal transport. In each of these fields, perfect control over 2D material properties including strain, doping, and heating is necessary, especially on the nanoscale. Here, we study clean devices consisting of membranes of single-layer MoS suspended on pillar arrays. Using Raman and photoluminescence spectroscopy, we have been able to extract, separate, and simulate the different contributions on the nanoscale and to correlate these to the pillar array design. This control has been used to design a periodic MoS mechanical membrane with a high reproducibility and to perform optomechanical measurements on arrays of similar resonators with a high-quality factor of 600 at ambient temperature, hence opening the way to multiresonator applications with 2D materials. At the same time, this study constitutes a reference for the future development of well-controlled optical emissions within 2D materials on periodic arrays with reproducible behavior. We measured a strong reduction of the MoS band gap induced by the strain generated from the pillars. A transition from direct to indirect band gap was observed in isolated tent structures made of MoS and pinched by a pillar. In fully suspended devices, simulations were performed allowing both the extraction of the thermal conductance and doping of the layer. Using the correlation between the influences of strain and doping on the MoS Raman spectrum, we have developed a simple, elegant method to extract the local strain in suspended and nonsuspended parts of a membrane. This opens the way to experimenting with tunable coupling between light emission and vibration.

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“…One of the interesting properties of 2D materials is that they can be scaled down to atomic thickness. Strain is easily induced in a thin MoS 2 channel by both substrate surface roughness and/or the high‐ k deposition process, resulting in MoS bond bending . Since the conduction and valence bands of MoS 2 are mainly composed of the energy splitting of the Mo d orbital, the band tail states will be easily introduced, as schematically illustrated in Figure b.…”

Section: Introductionmentioning

confidence: 99%

Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS₂ Field‐Effect Transistors

Fang

Toyoda

Taniguchi

et al. 2019

Adv Funct Materials

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2D materials are promising to overcome the scaling limit of Si field-effect transistors (FETs). However, the insulator/2D channel interface severely degrades the performance of 2D FETs, and the origin of the degradation remains largely unexplored. Here, the full energy spectra of the interface state densities (D it ) are presented for both n-and p-MoS 2 FETs, based on the comprehensive and systematic studies, i.e., full rage of channel thickness and various gate stack structures with h-BN as well as high-k oxides. For n-MoS 2 , D it around the mid-gap is drastically reduced to 5 × 10 11 cm −2 eV −1 for the heterostructure FET with h-BN from 5 × 10 12 cm −2 eV −1 for the high-k top-gate. On the other hand, D it remains high, ≈10 13 cm −2 eV −1 , even for the heterostructure FET for p-MoS 2 . The systematic study elucidates that the strain induced externally through the substrate surface roughness and high-k deposition process is the origin for the interface degradation on conduction band side, while sulfur-vacancy-induced defect states dominate the interface degradation on valance band side. The present understanding of the interface properties provides the key to further improving the performance of 2D FETs.

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Indirect Bandgap Puddles in Monolayer MoS₂ by Substrate‐Induced Local Strain

Cited by 136 publications

References 36 publications

Optical study of local strain related disordering in CVD-grown MoSe2 monolayers

Optical study of local strain related disordering in CVD-grown MoSe2 monolayers

Intrinsic Properties of Suspended MoS₂ on SiO₂/Si Pillar Arrays for Nanomechanics and Optics

Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS₂ Field‐Effect Transistors

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Indirect Bandgap Puddles in Monolayer MoS2 by Substrate‐Induced Local Strain

Cited by 136 publications

References 36 publications

Optical study of local strain related disordering in CVD-grown MoSe2 monolayers

Optical study of local strain related disordering in CVD-grown MoSe2 monolayers

Intrinsic Properties of Suspended MoS2 on SiO2/Si Pillar Arrays for Nanomechanics and Optics

Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS2 Field‐Effect Transistors

Contact Info

Product

Resources

About

Indirect Bandgap Puddles in Monolayer MoS₂ by Substrate‐Induced Local Strain

Intrinsic Properties of Suspended MoS₂ on SiO₂/Si Pillar Arrays for Nanomechanics and Optics

Full Energy Spectra of Interface State Densities for n‐ and p‐type MoS₂ Field‐Effect Transistors