Diamond Concise Annual Review 2021/22

18 19 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 2 1 / 2 2 D I A M O N D L I G H T S O U R C E A N N U A L R E V I E W 2 0 2 1 / 2 2 Structures and Surfaces Group T he Structures and Surfaces Group includes four beamlines, each consisting of multiple end-stations that are optimised for a specific type of experiment: I05 (Angle Resolved Photoelectron Spectroscopy – ARPES), I07 (Surface and Interface X-ray Diffraction), B07 (Versatile Soft X-ray Scattering – VERSOX), and I09 (Atomic and Electronic Structure of Surfaces and Interfaces). They offer a variety of techniques to examine the atomic scale structure, chemical nature and electronic state at buried interfaces or the surfaces of materials. The group continue to benefit from many key developments during remote working restrictions, such as enhanced automation, but recognise that many of themore complex studies rely on the expertise of the user groups, especially for sample preparation and experiment planning. It has also been a busy year for beamline upgrades and a strategic focus on outlining the facilities to be offered as part of the Diamond- II programme. The important role that surfaces and interfaces play in broader research areas such as battery technology, photovoltaic structures, and catalytic/electrochemical systems under operando conditions are key drivers for these developments. This year’s studies include improving the design and performance of industrial catalysts, developing energy efficient information technologies, and designing next generation electronic devices using 2D polymers. Improving catalyst design and performance Hydrogen spillover is an important phenomenon during catalysis which facilitates the improvement of hydrogen storage properties of porous nanomaterials and affects the reaction performance of multiphase catalytic reactions. It typically takes place over a metal on the support structure where a dihydrogen molecule undergoes dissociative chemisorption to form hydrogen atoms on the metal active centre, followed by the migration of atomic hydrogen from the metal surface to the catalytic support. To date, there has been no direct visualisation of this process at an atomic level, and the interchangeable pathway between the various hydrogen species on the metal/ support is still unknown. A team of researchers from the Wolfson Catalysis Centre at the University of Oxford investigated the process using the Versatile Soft X-ray (VerSoX) beamline B07, which can probe the oxidation state change of the catalyst in real-time andmonitored the change in concentration of the surface hydrogenic species on the support structure under reaction conditions. This is critical to determining the electronic structure and the surface composition of the catalyst. The results provide important guidance for the future improvement of hydrogenation catalysts. Wu S et al. DOI: 10.1021/jacs.1c02859 Developing energy efficient information technologies Mobile devices waste much energy in the form of heat. Our ever-growing need to access, process and store information makes it increasingly important that we develop new, more energy-efficient technologies. These are currently based on electron charge, but one avenue for future development is to use the electron spin - an intrinsic magnetic property of electrons - to achieve more energy-efficient information processing. Theoretical predictions suggest that certain magnetic materials exhibit spin polarised electrons at their surface with unusual ‘topological’ properties. In the future, such topological surface electrons might enable information processing without heat loss in electronic devices. An international team of researchers used Angle-Resolved Photoelectron Spectroscopy (ARPES) measurements on beamline I05 to verify these predictions. This allowed ARPES measurements with high energy resolution and a small beam spot. The experiments confirmed that the compounds MnBi 4 Te 7 and MnBi 6 Te 10 display spin-polarised, topological surface electrons. In the future, although significant challenges lie ahead, further optimisation of such materials could provide applications in electronic high-precision metrology (the scientific study of measurement) without the need for external magnetic fields. Vidal RC et al . DOI: 10.1103/PhysRevLett.126.176403 Designing new generation electronic devices Researchers continue to investigate new materials for potential applications in phototransistors, photodiodes, and memory devices. 2D polymers (2DPs) are a new generation of atomically/molecularly thin organic 2D materials, with repeated units linked via covalent bonds with long-range order in two distinct directions, that have recently emerged as interesting candidates in this area. Synthetic van der Waals heterostructures (vdWHs) are made by stacking different 2D crystals and offer great potential due to their tuneable physicochemical properties and designable functions. However, it has been challenging to synthesise structurally defined 2DPs and assemble them precisely with other 2D materials in a defined vdWH sequence. German researchers have now demonstrated a general but reliable on-water synthesis and assembly strategy for preparing large-area 2D polyimide-graphene vdWH. The team used Grazing Incidence Wide-Angle X-ray Scattering (GIWAXS) on the Surface and Interface Diffraction beamline I07 to demonstrate the successful formation of vdWHs. The on-water surface synthesis approach holds promise as a general method for preparing organic- inorganic vdWHs. Liu K et al. DOI: 10.1002/anie.202102984