Van der Waals Heterostructures of 2D Materials

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.

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. The potential of 2DMs implementation in various industries, ranging from optoelectronic ICT components to healthcare technologies, is described in the "European Science and Technology Roadmap for graphene, related two-dimensional crystals, and hybrid systems" [Nanoscale 7, 4598-4810 (2015)]. NGI has a very well developed network of collaborations with various industries where graphene and other 2DM are either being already implemented, or are at the R&D stage - this network will be used to disseminate the results developed in this project directly to the end users in the UK and Europe. At the same time, the UoM collaboration with Harvard and NUS has potential to attract interest of overseas businesses to Manchester, hence creating opportunities for the presence of US and Singaporean high-tech companies in the UK.

The importance of developing S&T of 2DM has been recognised both nationally and internationally. In the UK, EPSRC and Innovate UK have built a strong science base for 2DM through the multimillion infrastructure and research investments into the National Graphene Institute (NGI) and Graphene Engineering and Innovation Centre at Manchester, Graphene Centres at Cambridge and Exeter, 2DM growth at Harriot-Watt University, integrated with Henry Royce Institute for Advanced Materials, where the 2DM theme is one of major strands. In Europe, 2DM research is spearheaded by the H2020 Graphene Flagship Project (2013-2023, currently, 156 partners), and several 2DM centres of excellence have been formed around the world, including Centre for Advanced 2D Materials in Singapore (CA2DM), NSF-funded Center for 2-Dimensional & Layered Materials, and Science and Technology Center for Integrated Quantum Materials (CIQM) at Harvard, followed by a dozen of graphene and 2DM research and innovation centres in China.

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, thus, protecting the UK's long-term capability. The successful development of multi-functional 2D materials heterostructures and devices based on such materials will contribute towards the realisation of the EPSRC Delivery Plan. This project will build the new materials base to create Productive Nation, introducing the next generation of innovative and disruptive technologies (P1) by creating new materials with optolectronic functionalities. The proposed development of new materials for quantum technologies will support the development of Connected Nation, ensuring a safe and trusted cyber society (C4). The proposed development of healthcare applications of 2D materials will contribute to the optimisation of diagnostics (H3) and advance non-medicinal interventions (H5), support the EPSRC drive towards the Healthy Nation.

To broaden academic engagement, we will organise in Manchester two UK-US-Singapore Conferences '2D Materials Heterostructures' that will involve partners of Henry Royce Institute for Advanced Materials and the broader 2DM research community across the UK. For the broader dissemination, we will publish our new results in the high-impact journals (Science and Nature group magazines, where the applicants have published >20 paper in 2015-2018, since opening of NGI), as well as in topically focused venues, aiming at the golden open access publications for reaching a broader audience.