Spectroscopic evaluation of charge-transfer doping and strain in graphene/
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 heterostructures

Rao, Rahul; Islam, Ahmad E.; Singh, Simranjeet; Berry, Rajiv; Kawakami, Roland; Maruyama, Benji; Katoch, Jyoti

doi:10.1103/physrevb.99.195401

Cited by 75 publications

(86 citation statements)

References 58 publications

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“…46−50 More recently such a method has been adopted by some authors also for 1L MoS 2 . 40,41,51 In Figure 3a, the black open circles represent the A 1 ′ vs E′ pairs for all the Raman spectra collected on 1L MoS 2 on Au, while the blue open triangles represent the data pairs for 1L MoS 2 on Al 2 O 3 . The red and black lines represent the theoretical relations between the frequencies of the two vibrational modes at a laser wavelength of 532 nm in the ideal cases of a purely strained (strain line) and of a purely doped (doping line) 1L MoS 2 .…”

Section: Resultsmentioning

confidence: 99%

Strain, Doping, and Electronic Transport of Large Area Monolayer MoS₂ Exfoliated on Gold and Transferred to an Insulating Substrate

Panasci

Schilirò

Greco

et al. 2021

ACS Appl. Mater. Interfaces

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Gold-assisted mechanical exfoliation currently represents a promising method to separate ultralarge (centimeter scale) transition metal dichalcogenide (TMD) monolayers (1L) with excellent electronic and optical properties from the parent van der Waals (vdW) crystals. The strong interaction between Au and chalcogen atoms is key to achieving this nearly perfect 1L exfoliation yield. On the other hand, it may significantly affect the doping and strain of 1L TMDs in contact with Au. In this paper, we systematically investigated the morphology, strain, doping, and electrical properties of large area 1L MoS 2 exfoliated on ultraflat Au films (0.16−0.21 nm roughness) and finally transferred to an insulating Al 2 O 3 substrate. Raman mapping and correlative analysis of the E′ and A 1 ′ peak positions revealed a moderate tensile strain (ε ≈ 0.2%) and p-type doping (n ≈ −0.25 × 10 13 cm −2 ) of 1L MoS 2 in contact with Au. Nanoscale resolution current mapping and current−voltage (I−V) measurements by conductive atomic force microscopy (C-AFM) showed direct tunneling across the 1L MoS 2 on Au, with a broad distribution of tunneling barrier values (Φ B from 0.7 to 1.7 eV) consistent with p-type doping of MoS 2 . After the final transfer of 1L MoS 2 on Al 2 O 3 /Si, the strain was converted to compressive strain (ε ≈ −0.25%). Furthermore, an n-type doping (n ≈ 0.5 × 10 13 cm −2 ) was deduced by Raman mapping and confirmed by electrical measurements of an Al 2 O 3 /Si back-gated 1L MoS 2 transistor. These results provide a deeper understanding of the Au-assisted exfoliation mechanism and can contribute to its widespread application for the realization of novel devices and artificial vdW heterostructures.

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Section: Resultsmentioning

confidence: 99%

Strain, Doping, and Electronic Transport of Large Area Monolayer MoS₂ Exfoliated on Gold and Transferred to an Insulating Substrate

Panasci

Schilirò

Greco

et al. 2021

ACS Appl. Mater. Interfaces

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“…We noticed that for an individual MoS 2 flake on molten glass, (i) the Raman spectrum showed an E 2g at 385.2 cm −1 and an A 1g at 402.8 cm −1 with a difference of 17.6 cm −1 , smaller than that of monolayer MoS 2 grown on a SiO 2 /Si substrate, (ii) the A exciton peak located at 686.8 nm showed a red shift compared with MoS 2 grown on a SiO 2 /Si substrate. These changes may be ascribed to a strain effect and dielectric screening between the monolayer MoS 2 and molten glass [ 33–35 ], since after the flake was transferred onto a SiO 2 /Si substrate, the Raman peaks and A exciton of DP-grown MoS 2 are similar to those of exfoliated monolayer ones (Figs S12 and S13). To sum up, the above results indicate that the MoS 2 grown using the DP method is a uniform monolayer.…”

Section: Resultsmentioning

confidence: 99%

Dissolution-precipitation growth of uniform and clean two dimensional transition metal dichalcogenides

Cai

Lai

Zhao

et al. 2020

National Science Review

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Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have attracted much interest and shown promise in many applications. However, it is challenging to obtain uniform TMDCs with clean surfaces, because of the difficulties in controlling the way the reactants are supplied to the reaction in the current chemical vapor deposition (CVD) growth process. Here, we report a new growth approach called “dissolution-precipitation” (DP) growth, where the metal sources are sealed inside glass substrates to control their feeding to the reaction. Noteworthy, the diffusion of metal source inside glass to its surface provides a uniform metal source on the glass surface, and restricts the TMDC growth to only a surface reaction while eliminates unwanted gas-phase reaction. This feature gives rise to highly-uniform monolayer TMDCs with a clean surface on centimeter-scale substrates. The DP growth works well for a large variety of TMDCs and their alloys, providing a solid foundation for the controlled growth of clean TMDCs by the fine control of the metal source.

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“…PL spectra of the MoS 2 before and after assembling these two heterostructures (not shown here) also suggested the effects of compressive strain and hole doping in the MoS 2 , matching well the Raman spectral characteristics in Figure 8a. [224] One emerging group of vdW integrations is based on band alignment of individual semiconducting 2D materials, thereby allowing interlayer transitions or transfers (depending on the type of band alignment, as discussed below) between them, such that these vdW heterostructures are potentially useful in field of optoelectronics. Typically, two types of band alignment are possible, depending on the work functions of the component 2D materials.…”

Section: Optical Inspection Of Vdw Integration Of 2d Materialsmentioning

confidence: 99%

“…a) Correlation analysis of Raman spectral peak positions of graphene (𝜔 G , G band; 𝜔 G' , 2D band; left panel) and MoS 2 (𝜔 A' , A 1g mode; 𝜔 E' , E 12g mode; right panel) before (blue) and after (red) vdW integration. Reproduced with permission [224]. Copyright 2019, American Physical Society.…”

mentioning

confidence: 99%

Optical Inspection of 2D Materials: From Mechanical Exfoliation to Wafer‐Scale Growth and Beyond

et al. 2021

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Optical inspection is a rapid and non-destructive method for characterizing the properties of two-dimensional (2D) materials. With the aid of optical inspection, in situ and scalable monitoring of the properties of 2D materials can be implemented industrially to advance the development and progress of 2D material-based devices toward mass production. This review discusses the optical inspection techniques that are available to characterize various 2D materials, including graphene, transition metal dichalcogenides (TMDCs), hexagonal boron nitride (h-BN), group-III monochalcogenides, black phosphorus (BP), and group-IV monochalcogenides. First, the authors provide an introduction to these 2D materials and the processes commonly used for their fabrication. Then they review several of the important structural properties of 2D materials, and discuss how to characterize them using appropriate optical inspection tools. The authors also describe the challenges and opportunities faced when applying optical inspection to recently developed 2D materials, from mechanically exfoliated to wafer-scale-grown 2D materials. Most importantly, the authors summarize the techniques available for largely and precisely enhancing the optical signals from 2D materials. This comprehensive review of the current status and perspective of future trends for optical inspection of the structural properties of 2D materials will facilitate the development of next-generation 2D material-based devices.

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Spectroscopic evaluation of charge-transfer doping and strain in graphene/ MoS2 heterostructures

Cited by 75 publications

References 58 publications

Strain, Doping, and Electronic Transport of Large Area Monolayer MoS₂ Exfoliated on Gold and Transferred to an Insulating Substrate

Strain, Doping, and Electronic Transport of Large Area Monolayer MoS₂ Exfoliated on Gold and Transferred to an Insulating Substrate

Dissolution-precipitation growth of uniform and clean two dimensional transition metal dichalcogenides

Optical Inspection of 2D Materials: From Mechanical Exfoliation to Wafer‐Scale Growth and Beyond

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Spectroscopic evaluation of charge-transfer doping and strain in graphene/ MoS2 heterostructures

Cited by 75 publications

References 58 publications

Strain, Doping, and Electronic Transport of Large Area Monolayer MoS2 Exfoliated on Gold and Transferred to an Insulating Substrate

Strain, Doping, and Electronic Transport of Large Area Monolayer MoS2 Exfoliated on Gold and Transferred to an Insulating Substrate

Dissolution-precipitation growth of uniform and clean two dimensional transition metal dichalcogenides

Optical Inspection of 2D Materials: From Mechanical Exfoliation to Wafer‐Scale Growth and Beyond

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Product

Resources

About

Strain, Doping, and Electronic Transport of Large Area Monolayer MoS₂ Exfoliated on Gold and Transferred to an Insulating Substrate

Strain, Doping, and Electronic Transport of Large Area Monolayer MoS₂ Exfoliated on Gold and Transferred to an Insulating Substrate