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Understanding the properties of van der Waals heterostructures from transmission electron microscopy imaging

Department of Materials

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Dr S Haigh , Prof A Geim Applications accepted all year round

About the Project

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 moire superlattices [2], to creating a totally new concept of designer nanochannels for molecular or ionic transport [3]. The impressive progress in understanding these phenomena and creating ideal conditions for their observation crucially depends on our knowledge of the atomic-resolution structure of the heterostructures. For example, in the case of new artificial crystals we need to know the structure and composition of buried interfaces between dissimilar atomic layers, while in the case of nanochannels created by leaving atomically-thin spaces between joined together 2D blocks, the required information is the quality of the channel ‘walls’ and the structure of the confined substance. Thanks to the extreme thinness of 2D heterostructures, such information can be obtained using transmission electron microscopy, either in the usual planar geometry, or in cross-section [4].

In this project you will analyse 2D heterostructures made either from dissimilar atomically thin layers (artificial 2D crystals) or put together to create specially designed nanochannels (dubbed ‘2D nothing’). These artificial crystals are fabricated by assembly of monolayers extracted from layered crystals (for example, graphene, insulating hexagonal boron nitride, semiconducting transition-metal chalcogenides, ferromagnetic CrI3 or superconducting NbSe2). The University of Manchester’s National Graphene Institute contains all the state-of-the art microfabrication facilities that will be needed for this project, including recently commissioned glove-box exfoliation and transfer systems. The Department of Materials has a suite of cutting edge transmission electron microscopy (TEM) facilities that you will use to study their atomic structure and combine this with the results of other measurements (electronic or mass transport) to reveal and understand the underlying phenomena. The new knowledge will then be applied to optimise the structure and properties of new nanodevices.

Among the many challenging problems that this approach can be expected to solve, the initial focus will be on:
(i) Understanding the atomic structure of buried interfaces in artificial crystals with twisted component layers. This can be expected to help solve the rich and unusual physics found in such systems.

(ii) Revealing the structure of liquids confined in atomically thin 2D channels. This has generate huge excitement but the precise structure of such systems is still far from clear and of huge importance to microfluidic, biology, environmental separations.

In this project you will acquire a broad range of microfabrication and characterisation experimental skills. The specific challenges can be adapted depending on the interests of the student. There will be opportunities to undertake experiments at national and international facilities, and to present your work at world leading international conferences.

Funding Notes

Funding support is available for suitably qualified UK and EU applicants. International applicants should contact the main supervisor to discuss potential funding opportunities.

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