Theory of thin-film-mediated exfoliation of van der Waals bonded layered materials

Sun, Haoye; Sirott, Eric W.; Mastandrea, James P.; Gramling, Hannah M.; Zhou, Yuzhi; Poschmann, Max; Taylor, Hayden; Ager, Joel W.; Chrzan, D. C.

doi:10.1103/physrevmaterials.2.094004

Cited by 21 publications

(23 citation statements)

References 24 publications

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“…[ 7a ] This has recently been rationalized theoretically, showing that both tensile and compressive biaxial strains induced by the substrate promote monolayer exfoliation due to the energetically unfavorable disruption of the interlayer AB stacking registry in bulk MoS 2 . [ 17 ] Our data suggest that the oxide‐free Au surface facilitates uniform strain and therefore binding with MoS 2 wherever the two materials are in contact. Conversely, the larger strain dispersion on Ag and Pt reflects their higher susceptibility to oxidation and potentially spatial heterogeneity of the strain.…”

Section: Figurementioning

confidence: 90%

The Intricate Love Affairs between MoS₂ and Metallic Substrates

Velický

Donnelly

Hendren

et al. 2020

Adv Materials Inter

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Mechanical exfoliation of 2D materials yields high-quality crystals popular with researchers in fundamental scientific disciplines but its scalability is severely limited. This method generates 2D monolayers tens or hundreds of microns in lateral sizes on most substrates, often after an elaborate surface treatment. [1] Gold-mediated exfoliation of chalcogenides, chlorides, thiophosphates, black phosphorus, and black arsenic, with a robust control of the near-unity monolayer yield at a millimeter-/centimeterscale, has recently emerged as a viable solution to the scalability issues, [2] and has been adopted in various branches of applied research and engineering. [3] In the case of transition metal dichalcogenides (TMDCs), the root of the preferential mono layer exfoliation has been attributed to the strong interactions between gold and chalcogenides, which have been explored in different facets of science for decades. [4] However, it has recently been shown that the interaction between TMDCs and Au is non-covalent and van der Waals (vdW) in its nature, inferred from the sizeable S-Au equilibrium distance (3.5 Å) and binding energies in the Au-MoS 2 heterostructure. [2c,5] The vdW interaction therefore facilitates the transfer of the TMDC monolayers onto non-metallic substrates, which restore their semiconducting characteristics exploitable in optoelectronics, photovoltaics, and related themes. [2b] The polymer-free nature of this transfer, which leaves surfaces free from residual contamination, is of significant advantage also. [6] Despite these research efforts, it is currently unknown whether this method can also be applied to other metals, predicted to exhibit even stronger binding with MoS 2 than Au. [7] Here, we study the ability of different metallic substrates to exfoliate large-area monolayer MoS 2. We find that gold is by far the best substrate, outperforming all other metals by at least two orders of magnitude in terms of the lateral size of the MoS 2 , thanks to the unique ability of Au to resist oxidation and the sizeable interfacial strain in the Au-MoS 2 heterostructure. A moderate exfoliation yield is achieved for other precious metals, including Pt, Pd, and Ag, while hardly any exfoliated material is found on base metals, including Cu, Ni, Co, Cr, and Ti, which suffer from significant oxidation of their surface upon exposure to air. A correlation between the maximum lateral Mechanical exfoliation yields high-quality 2D materials but is challenging to scale up due to the small lateral size and low yield of the exfoliated crystals. Gold-mediated exfoliation of macroscale monolayer MoS 2 and related crystals addresses this problem. However, it remains unclear whether this method can be extended to other metals. Herein, mechanical exfoliation of MoS 2 on a range of metallic substrates is studied. It is found that Au outperforms all the other metals in their ability to exfoliate macroscale monolayer MoS 2. This is rationalized by gold's ability to resist oxidation, which is compromised on other metals a...

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Section: Figurementioning

confidence: 90%

The Intricate Love Affairs between MoS₂ and Metallic Substrates

Velický

Donnelly

Hendren

et al. 2020

Adv Materials Inter

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“…The umbrella sampling technique was introduced by Torrie and Valleau 37 , to improve the sampling of systems with energy landscapes containing high energy barriers. The weighted histogram analysis method 38 can be used to analyze a series of umbrella sampling methods. In the transition interface sampling 39 , the transition region is divided into subregions of intermediate states.…”

Section: First-principles Calculationsmentioning

confidence: 99%

“…These potentials allow the realization of the thermodynamic stability of graphene-based materials under different conditions, environmental chemistry, substrate, interlayer interactions, and structural defects. However, only a few of them have been employed in the study of computational synthesis of other 2D materials to reveal thermodynamic stability, simulate the process of the growth of layers, model the top-down synthesis of 2D materials such as exfoliation techniques 38 , and evaluate the properties of 2D nanostructures. This is due to several challenges including the following: (1) the long time required to develop a reactive potential, (2) the nontransferability of potential parameters from one material to another, and (3) the lack of universal functional forms for the reactive potentials.…”

Section: Molecular Dynamicsmentioning

confidence: 99%

Multiscale computational understanding and growth of 2D materials: a review

et al. 2020

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The successful discovery and isolation of graphene in 2004, and the subsequent synthesis of layered semiconductors and heterostructures beyond graphene have led to the exploding field of two-dimensional (2D) materials that explore their growth, new atomic-scale physics, and potential device applications. This review aims to provide an overview of theoretical, computational, and machine learning methods and tools at multiple length and time scales, and discuss how they can be utilized to assist/guide the design and synthesis of 2D materials beyond graphene. We focus on three methods at different length and time scales as follows: (i) nanoscale atomistic simulations including density functional theory (DFT) calculations and molecular dynamics simulations employing empirical and reactive interatomic potentials; (ii) mesoscale methods such as phase-field method; and (iii) macroscale continuum approaches by coupling thermal and chemical transport equations. We discuss how machine learning can be combined with computation and experiments to understand the correlations between structures and properties of 2D materials, and to guide the discovery of new 2D materials. We will also provide an outlook for the applications of computational approaches to 2D materials synthesis and growth in general.npj Computational Materials (2020) 6:22 ; https://doi.

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“…Instead, uniform strain is the determining factor and other metals that do not produce such uniform strain are unable to exfoliate large-area ML TMDs. [26,27] Given that there are more than 800 layered crystals are predicted to form ML flakes by exfoliation [28] of which only ≈40 2D materials have been realized, [12] a study and demonstration of other metalmediated large-area exfoliation is important for the practical realization of many future 2D materials.…”

mentioning

confidence: 99%

Can Metals Other than Au be Used for Large Area Exfoliation of MoS₂ Monolayers?

Johnston

Khondaker

2022

Adv Materials Inter

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Au‐mediated exfoliation of 2D transition‐metal dichalcogenides (TMDs) has received significant attention due to its ability to produce large‐area monolayer (ML) flakes. This process has been attributed to strong TMD/Au binding energy (BE) as well as the uniform strain between the TMDs and Au. However, large‐area exfoliation of TMDs with other metals that have even stronger theoretical BE than Au/TMD is not successful, leading to question whether the BE plays any role in the exfoliation process. Here, successful demonstration of large‐area ML MoS2 using Cu, Ni, and Ag with various predicted strain, including Pd with almost no strain, but stronger BE than Au/MoS2 is demonstrated. Optical micrographs show MoS2 flakes with 100s of µm in size with a yield of several tens to hundreds of ML flakes per exfoliation. Photoluminescence and Raman spectroscopy confirm the ML nature of the flakes, while electrical transport measurements show mobilities of ≈6 cm2 V−1 s−1 with a current on‐off ratio ≈108 consistent with high‐quality ML MoS2. Given that MoS2 can be exfoliated with metals that have strong BE irrespective of their strain values suggests that BE is the primary mechanism in successful exfoliation of large‐area ML MoS2.

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Theory of thin-film-mediated exfoliation of van der Waals bonded layered materials

Cited by 21 publications

References 24 publications

The Intricate Love Affairs between MoS₂ and Metallic Substrates

The Intricate Love Affairs between MoS₂ and Metallic Substrates

Multiscale computational understanding and growth of 2D materials: a review

Can Metals Other than Au be Used for Large Area Exfoliation of MoS₂ Monolayers?

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Theory of thin-film-mediated exfoliation of van der Waals bonded layered materials

Cited by 21 publications

References 24 publications

The Intricate Love Affairs between MoS2 and Metallic Substrates

The Intricate Love Affairs between MoS2 and Metallic Substrates

Multiscale computational understanding and growth of 2D materials: a review

Can Metals Other than Au be Used for Large Area Exfoliation of MoS2 Monolayers?

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The Intricate Love Affairs between MoS₂ and Metallic Substrates

The Intricate Love Affairs between MoS₂ and Metallic Substrates

Can Metals Other than Au be Used for Large Area Exfoliation of MoS₂ Monolayers?