The isolation of single-atomic layer graphene has led to a surge of interest in other layered crystals with strong in-plane bonds and weak, van der Waals-like, interlayer coupling. A variety of two-dimensional (2D) crystals have been investigated, including large band gap insulators and semiconductors with smaller band gaps such as transition metal dichalcogenides. Interest in these systems is motivated partly by the need to combine them with graphene to create field effect transistors with high on-off switching ratios. More importantly, heterostructures made by stacking different 2D crystals on top of each other provide a platform for creating new artificial crystals with potential for discoveries and applications. The possibility of making van der Waals heterostructures has been demonstrated experimentally only for a few 2D crystals. However, some of the currently available 2D layers are unstable under ambient conditions, and those that are stable offer only limited functionalities, i.e. low carrier mobility, weak optical emission/absorption, band gaps that cannot be tuned, etc. In a recent series of pilot experiments, we have demonstrated that nanoflakes of the III-VI layer compound, InSe, with thickness between 5 and 20 nanometers, have a "thickness-tuneable" direct energy gap and a sufficiently high chemical stability to allow us to combine them with graphene and related layer compounds to make heterostructures with novel electrical and optical properties. The main goal of this project is to develop graphene-hybrid heterostructures based on this novel class of two-dimensional (2D) III-VI van der Waals crystals. This group of semiconductors will enrich the current "library" of 2D crystals by overcoming limitations of currently available 2D layers and by offering a versatile range of electronic and optical properties. From the growth and fabrication of new systems to the demonstration of prototype devices, including vertical tunnel transistors and optical-enhanced-microcavity LEDs, our project will provide a platform for scientific investigations and will contribute to the technology push required to create new routes to device miniaturization, fast-electronics, sensing and photonics. There is great potential for further growth of all these sectors as the fabrication of 2D systems improves and as new properties are discovered and implemented in functional devices.

The progressive miniaturization of materials and devices in the 21st century has enabled important discoveries and access to a wide range of phenomena of fundamental and applied interest. But future progress and innovative solutions to global challenges require a shift towards transformative material systems and integration technologies. Here we propose to establish at the University of Nottingham a facility (EPI2SEM) for the EPItaxial growth and in-situ analysis of a new generation of 2-dimensional SEMiconductors based on metal chalcogenides. Their unique electronic properties (tuneable band structure, IR-VIS-UV broad optical absorption, electron correlations, high electron mobility, etc.) and versatility for a wide range of applications (digital flexible electronics, optoelectronics, quantum technologies, energy, etc.) have attracted a surge of interest worldwide. However, for these new materials to meet academia and industry needs, several challenges must be addressed, including their controlled scalable growth, investigation by advanced techniques, and integration in complex device architectures. EPI2SEM will provide the UK community with a unique capability for the development of semiconductors grown with atomic layer precision in a clean ultra high vacuum system with fully-characterised electronic, chemical and morphological properties for advances across several research disciplines. EPI2SEM will enable the transformative miniaturization and functionalization of semiconductors for advances in condensed matter (quantum materials), manufacturing (new processes and designs), quantum technologies (security, sensing, communication), nanotechnologies (low-energy consumption, diversification, integration), surface physics (sensing, catalysis, energy conversion). Progress in these areas is key to the health of several research disciplines (engineering, medicine, chemistry, biology, etc.) contributing towards prosperity outcomes. The future competitiveness of the UK economy relies on innovation in science; ability to respond timely to global changes/challenges through innovation in infrastructure; the availability of highly-skilled and trained scientists and technologists; and flexibility to exploit novel technologies and materials to deliver better quality of life. This proposal has the potential to deliver innovation across these areas, addressing several challenges facing society. In particular, EPI2SEM will contribute to address the EPSRC priority of "21st Century Materials". In 2013, David Willetts announced the Eight Great Technologies that will propel the UK to future growth. This includes "Advanced Materials and Nanotechnology" that led to the establishment of the Henry Royce Institute (NGI) and the National Graphene Institute (NGI). One of the research pillars of the HRI/NGI is "2D Materials", but methods for their manufacturing need to be developed. The new equipment will set out the key steps needed to reach a long-term vision and benefit strategically important research areas, as set out in the 2018 government industrial strategy White paper.