Van der Waals Heterostructures of 2D Materials

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The advent of 2D materials (2DM), pioneered in the UK with the discovery of graphene at the University of Manchester, has opened a new avenue in materials science. Derived from bulk layered crystals with covalent intra-layer bonds and a weak van der Waals (vdW) interlayer coupling, 2DM offer an opportunity to create new hybrid "materials on demand" with properties tailored to particular applications, by combining different atomically thin layers into heterostructures. The family of such crystals includes graphene, hexagonal boron nitride (hBN), phosphorene, transition metal dichalcogenides (TMD, such as MoS2, MoSe2, WS2,WSe2, NbSe2, etc), post-transition metal chalcogenides (InSe, GaSe), metal tri-halides (CrI3, CrBr3, CrCl3), among many others already separated from bulk crystals by mechanical exfoliation, or grown epitaxially in the form of monolayer or bilayer crystals. Collectively, these van der Waals materials cover a wide range of properties, from conductive to insulating, from transparent to opaque, from diamagnetic to ferromagnetic, from mechanically stiff to compliant, and their heterostructures have already been shown to offer various appealing functionalities including tunnelling transistors, light emitting diodes, photodetectors, and various sensors. The opportunities created by this new approach to materials discovery are almost endless, as proven by dozens of research and proof-of-concept publications appearing in academic press daily and hundreds of patents annually. In order to speed up the new materials discovery and optimise the choice of materials in heterostructures, at National Graphene Institute we use 'atomic LEGO' approach by creating heterostructures of 2D layers lifted from bulk crystals to understand their properties and, then, to create bespoke devices where several functionalities (e.g., optoelectronic or/and sensing) are combined within only few nanometre thickness of the hybrid material. This way, we are able to identify quickly and cost efficiently the promising systems for applications, so that those could be later studied subject to the top-down mass production methods (such as printing from inks, CVD or MBE growth). By combining the unique expertise and capability of NGI with complementary expertise and capabilities of C2DM and CIQM, NGI will secure UK's world-leading position in 2DM S&T for the next decade.