Unusual Stacking Variations in Liquid-Phase Exfoliated Transition Metal Dichalcogenides

Shmeliov, Aleksey; Shannon, M. D.; Wang, Peng; Kim, Judy; Okunishi, Eiji; Nellist, Peter D.; Dolui, Kapildeb; Sanvito, Stefano; Nicolosi, Valeria

doi:10.1021/nn5003387

Cited by 44 publications

(48 citation statements)

References 55 publications

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“…This links directly with previous ex situ reports on in-layer polymorphism 12−15 and co-existence of various stacking types 17,18,21,22 in ex situ processed MoS 2 , including chemical synthesis and CVD. As a second and equally important point, our in situ data now clarify that the structural evolution of the MoS 2 leading to such polymorphism is not static but highly dynamic, where phases appear/disappear and transform into each other over time.…”

Section: Resultssupporting

confidence: 87%

“…Instead the measured atomically resolved intensity profile of spot (c) at 17 min is consistent with a bilayer that shows homonuclear stacking (either 2H′ or 1H), 17 where Mo atoms of the second layer are placed directly above Mo atoms of the first layer. This observation of homonuclear stacking next to 2H stacking suggests that, besides crystallization toward equilibrium 2H, initial a-MoS 2 can also crystallize into other MoS 2 polymorphs under fixed processing conditions, thereby resulting in co-existence of several MoS 2 polymorphs.…”

Section: Resultsmentioning

confidence: 65%

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Atomic-Scale in Situ Observations of Crystallization and Restructuring Processes in Two-Dimensional MoS₂ Films

et al. 2018

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We employ atomically resolved and element-specific scanning transmission electron microscopy (STEM) to visualize in situ and at the atomic scale the crystallization and restructuring processes of two-dimensional (2D) molybdenum disulfide (MoS2) films. To this end, we deposit a model heterostructure of thin amorphous MoS2 films onto freestanding graphene membranes used as high-resolution STEM supports. Notably, during STEM imaging the energy input from the scanning electron beam leads to beam-induced crystallization and restructuring of the amorphous MoS2 into crystalline MoS2 domains, thereby emulating widely used elevated temperature MoS2 synthesis and processing conditions. We thereby directly observe nucleation, growth, crystallization, and restructuring events in the evolving MoS2 films in situ and at the atomic scale. Our observations suggest that during MoS2 processing, various MoS2 polymorphs co-evolve in parallel and that these can dynamically transform into each other. We further highlight transitions from in-plane to out-of-plane crystallization of MoS2 layers, give indication of Mo and S diffusion species, and suggest that, in our system and depending on conditions, MoS2 crystallization can be influenced by a weak MoS2/graphene support epitaxy. Our atomic-scale in situ approach thereby visualizes multiple fundamental processes that underlie the varied MoS2 morphologies observed in previous ex situ growth and processing work. Our work introduces a general approach to in situ visualize at the atomic scale the growth and restructuring mechanisms of 2D transition-metal dichalcogenides and other 2D materials.

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Section: Resultssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 65%

Atomic-Scale in Situ Observations of Crystallization and Restructuring Processes in Two-Dimensional MoS₂ Films

et al. 2018

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“…Furthermore, our results provide another perspective on previous works 23,24 which showed tunability of the bandgap via tensile strain in the MoS 2 layer, and contributes to an increasing body of work that exploits different stacking registries for discovering useful electronic properties (e.g., Ref. 46).…”

supporting

confidence: 62%

Tunable MoS2 bandgap in MoS2-graphene heterostructures

Ebnonnasir

Narayanan

Kodambaka

et al. 2014

Applied Physics Letters

158

111

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Using density functional theory calculations with van der Waals corrections, we investigated how the interlayer orientation affects the structure and electronic properties of MoS2-graphene bilayer heterostructures. Changing the orientation of graphene with respect to MoS2 strongly influences the type and the value of the electronic bandgap in MoS2, while not significantly altering the binding energy between the layers or the interlayer spacing. We show that the physical origin of this tunable bandgap arises from variations in the S–S interplanar distance (MoS2 thickness) with the interlayer orientation, variations which are caused by electron transfer away from the Mo–S bonds.

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“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 no severe structural damage to the MoS 2 was induced by our functionalization sequence. We note that an analysis of 2H and 1T polytype content from bright field images is extremely challenging 51 and beyond the scope of the manuscript. XPS furthermore suggests that the degree of functionalization is 20%.…”

Section: Dispersibility and Structural Integrity Of The Latticementioning

confidence: 99%

Basal-Plane Functionalization of Chemically Exfoliated Molybdenum Disulfide by Diazonium Salts

et al. 2015

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Although transition metal dichalcogenides such as MoS2 have been recognized as highly potent two-dimensional nanomaterials, general methods to chemically functionalize them are scarce. Herein, we demonstrate a functionalization route that results in organic groups bonded to the MoS2 surface via covalent C-S bonds. This is based on lithium intercalation, chemical exfoliation and subsequent quenching of the negative charges residing on the MoS2 by electrophiles such as diazonium salts. Typical degrees of functionalization are 10-20 atom % and are potentially tunable by the choice of intercalation conditions. Significantly, no further defects are introduced, and annealing at 350 °C restores the pristine 2H-MoS2. We show that, unlike both chemically exfoliated and pristine MoS2, the functionalized MoS2 is very well dispersible in anisole, confirming a significant modification of the surface properties by functionalization. DFT calculations show that the grafting of the functional group to the sulfur atoms of (charged) MoS2 is energetically favorable and that S-C bonds are formed.

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Unusual Stacking Variations in Liquid-Phase Exfoliated Transition Metal Dichalcogenides

Cited by 44 publications

References 55 publications

Atomic-Scale in Situ Observations of Crystallization and Restructuring Processes in Two-Dimensional MoS₂ Films

Atomic-Scale in Situ Observations of Crystallization and Restructuring Processes in Two-Dimensional MoS₂ Films

Tunable MoS2 bandgap in MoS2-graphene heterostructures

Basal-Plane Functionalization of Chemically Exfoliated Molybdenum Disulfide by Diazonium Salts

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Unusual Stacking Variations in Liquid-Phase Exfoliated Transition Metal Dichalcogenides

Cited by 44 publications

References 55 publications

Atomic-Scale in Situ Observations of Crystallization and Restructuring Processes in Two-Dimensional MoS2 Films

Atomic-Scale in Situ Observations of Crystallization and Restructuring Processes in Two-Dimensional MoS2 Films

Tunable MoS2 bandgap in MoS2-graphene heterostructures

Basal-Plane Functionalization of Chemically Exfoliated Molybdenum Disulfide by Diazonium Salts

Contact Info

Product

Resources

About

Atomic-Scale in Situ Observations of Crystallization and Restructuring Processes in Two-Dimensional MoS₂ Films

Atomic-Scale in Situ Observations of Crystallization and Restructuring Processes in Two-Dimensional MoS₂ Films