Periodic Reporting for period 2 - LATO (Large-Area Transparent Opto-Electronics using 2D Materials) Reporting period: 2018-10-01 to 2020-03-31 Summary of the context and overall objectives of the project Research in 2D materials has increased dramatically since the first isolation of graphene in 2004, with diverse interdisciplinary studies. In the last few years, 2D material research expanded beyond graphene by the development of other 2D materials, such as monolayered transition metal dichalcogenides, black phosphorous, and Boron Nitride. There are hundreds of possible 2D crystals that can be isolated, with properties ranging from metallic, semi-metallic, semiconducting to insulating, depending on the material composition. Semiconducting 2D materials have attracting interest in next-generation electronics/opto-electronics such as transistors, photo-gated transistors, photo-detectors, solar cells, and light emitting devices (LEDs), molecular sensors and optical imaging sensors. The unique structural form of 2D materials provides several benefits over other existing materials: ultrathin, flexible, highly transparent, large surface to volume ratio, and 2D quantum confinement. High transparency LEDs are required for applications in transparent displays on glass panels. Many 2D based opto-electronic devices have used mechanical exfoliation from bulk crystals, but this is limited to small areas. Recent work on chemical vapour deposition (CVD) to grow wafer-scale 2D materials has opened up exciting opportunities for commercial exploitation and has accelerated the intensity of research in this field towards real applications. The vision of this proposal is to realize a new class of ultra-thin, flexible, large-area, transparent, high-sensitivity opto-electronic device arrays based on all 2D materials, with a focus on imaging sensors and LEDs. This will involve wafer-scale CVD synthesis of 2D materials including novel blue and green 2D semiconductors, optical spectroscopy to probe the interlayer interactions, atomic level structure-property correlations using advanced electron microscopy, and the nanoscale fabrication and testing of high efficiency devices. Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far 2D materials have been grown using chemical vapour deposition methods to expand the catalogue of available materials for semiconductor applications. This has included, graphene, hBN, MoS2, WS2, SnS2, PbI2, PdSe2, PtSe2, ReS2, and GaS. These variants of 2D materials have properties that expand metallic, semiconducting to insulating and this enabled the fabrication of ultrathin opto-electronics. The high performance light emitting devices were created with wafer scale uniformity, using layer by layer transfer, into a vertical tunnelling form. The mechanisms for degradation were elucidated, revealing thermally induced reactions with oxygen. A UV discriminating photodetector was produced using GaS and showed no response to visible light. Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far) I have now terminated the project as I am leaving the UK to a new position in the USA. All 2D ultrathin photodetector
