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mmc2021 Abstract Database

Atomic Imaging in 2D Material Heterostructures : Twist, Defects and Particle Synthesis

Atomic Imaging in 2D Material Heterostructures : Twist, Defects and Particle Synthesis

Session

Stream 1: EMAG - 2D Materials

Authors

Prof Sarah Haigh (2), Dr Nick Clark (2), Astrid Weston (2), Dr Daniel Kelly (2), Dr Matthew Hamer (2), Dr Yichao Zou (2), Dr Vladimir Enaldiev (2), Dr Alex Summerfield (2), Dr Victor Zólyomi (2), Prof Denis Gebauer (1), Prof Vladimir Falko (2), Dr Roman Gorbachev (2)

Affiliations

1. Institute of Inorganic Chemistry, Leibniz Universität Hannover
2. National Graphene Institute, University of Manchester

Keywords

2D materials, CaCO3, scanning transmission electron microscopy, in situ, liquid cell, graphene, transition metal dichalcogenides

Abstract text

This talk aims to demonstrate how atomic resolution scanning transmission electron microscope (STEM) imaging is being used in Manchester to support and enable the development of 2D materials and their heterostructures. The possibility to create new ‘designer’ materials by stacking together atomically thin layers extracted from layered materials with different properties has opened up a huge range of opportunities, from new optoelectronic phenomena [1], modifying and enhancing electron interactions in moiré superlattices [2], to creating a totally new concept of designer nanochannels for molecular or ionic transport [3]. The impressive progress being achieved in the field crucially depends on knowledge of the atomic structure of these heterostructures [4], which in many cases can only be analysed by transmission electron microscopy (TEM) techniques. In this talk I will try to illustrate this with some of our recent work. I will demonstrate imaging of the unusual lattice reconstruction that occurs in twisted transition metal dicholcogenide bilayers [5]. We reveal that this behaviour is more complex than is seen for twisted heterostructures of graphene and/or hexagonal boron nitride. Complementary scanning probe microscopy (SPM) measurements show that such reconstruction creates strong piezoelectric textures, opening a new avenue for engineering of 2D material properties. I will also illustrate a new TEM support grid where an MoS₂ wetting layer is added to improve adhesion, enabling sample transfer and TEM visualisation for even the most challenging 2D heterostructures [6]. Finally I will show that 2D heterostructures can themselves be used to enable new possibilities for STEM imaging. We present a new design of graphene based mixing cell where a monolayer 2D material membrane is fractured by the electron beam enabling the earliest stages of mixing to be observed. We apply this novel platform for the direct visualisation of the entire reaction timeline for calcium carbonate synthesis, including nanoscale imaging of liquid-liquid phase separation, the formation of amorphous calcium carbonate, and particle crystallization. [7]

References

[1] J. Zultak et al, Nature Communications 11 (1), 1-6 (2020), [2] R. Krishna-Kumar et al, Science 357, 181-184 (2017); [3] B. Radha et al. Nature 538, 222–225 (2016) and Keerthi, et al Nature 558 (7710), 420-424. (2018) [4] D. Hopkinson et al, ASC Nano 13 (5), 5112-5123 (2019), [5] A. Weston et al Nature Nanotechnology, 15 592–597 (2020), [6] M. Hamer et al, Nano Letters, 20, 9, 6582–6589 (2020). [7] D. Kelly, N. Clark et al, Advanced Materials, in press (2021)