Diamond Light Source - Annual Review 2022/23

26 27 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 2 / 2 3 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 2 / 2 3 for the soft X-ray ARPES system is now complete and the momentum microscope analyser has started to be commissioned. This is a novel design with the first k space images of dispersion from gold being realised in March 2023. Extensive commissioning is required to optimise the voltages on all of the (more than 40) lens elements to make the system available for user operation. This instrument will complement the ARPES facilities available at I05, working at higher energies and improving the ability to probe buried or true bulk electronic states and their k z dependence. I09 also took delivery of a small spot ultraviolet photoelectron spectroscopy (UPS) system that is essential to develop the momentum microscope to reach its ultimate resolution without having to use the synchrotron beam. Concurrently, the software to drive the analyser is being developed with the detector manufacturer, to ensure that it is maintainable and can be driven by the Diamond control system. Smaller projects, focusing on delivering a more robust sample manipulator are ongoing with assembly and commissioning underway. A wide research programme is supported by I09, ranging from surface science experiments on molecular adsorption or single atom catalysts through to conventional and solid state battery studies. The group are enhancing the associated infrastructure available, including the design of a new offline ultrahigh vacuum system to characterise samples, a proposal that was well received by the Scientific Advisory Committee (SAC). Design work has started on a small part of this system that will initially be operated as a basic standalone chamber. This continues to be a high priority that will position Diamond to be able to rapidly study new samples and enhance the link between laboratory and synchrotron based experiments.We plan for this capability to be at the core of many of the joint PhD studentships that we support. The variety of science undertaken within the group is very large, underpinning fundamental surface science investigations through to understanding the relevance to real-world applications. The user highlights include how I05 has been used to study ‘misfit compounds’ formed from stacked two-dimensional materials with no epitaxial relationships between the layers. The influence on the electron bands caused by the misfit can be probed using the small spot of nanoARPES branch. A different type of disorder is highlighted in the work from I09, where the structure of g -Ga 2 O 3 has been studied. This material has many potential uses in sensors, solar cells and electronics but can exist in a large number of phases that must be understood to fully exploit and engineer them. On I07 researchers probed how sulfobetaines are incorporated into a lipid bilayer that mimics a cell membrane finding that the roughness increases together with other significant structural changes at higher concentrations. The role of these molecules as potential drug-delivery agents is outlined in this research. The work on B07 (Branch C) has utilised the tunability of the photon source to use resonant XPS to study ionic liquids and how they perform when a voltage is applied to probe their use in electrochemical storage devices. The ability to probe a particular element ( e.g. cobalt) has enabled real detail to be added to the understanding in these systems. The highlight for B07 (Branch B) has focused on the other main technique available at the beamline, NEXAFS, which was used to understand co-crystallisation in a two-component system to understand how such materials could be used in future drug delivery processes that could tailor drug-release profiles. The members of the Structures and Surfaces group are committed to continue offering the best support to our users, to ensure the highest quality scientific output from the beamlines. The combination of strong interactions and collaborations, together with continuous improvements to the instrumentation, software and technique development is key to our success. Please contact us if youwould like to discuss any of the possibilities that we offer and how such synchrotron based studies could help in your research. Structures and Surfaces Group Chris Nicklin, Science Group Leader T his year has beenanother exceptionally busy year for the Structures and Surfaces group, with thenumber of on-siteuser visits returning topre- pandemic levels,whilst theexperiments becomeevermore complex. In-situ and operando studies havebeena real focus for thegroup,whether it is straining a sample for electronic structure measurements, employing ‘realistic’ conditions to study catalytic processes or understanding the processes occurring under electrochemical control amongst many others. Many of these developments have been undertaken collaboratively with key groups, but with the resulting environments being made available to all users. Increasingly, developments are being undertaken across the group and with other groups to ensure consistent approaches that will benefit the user community; for example, we have just started a new ultrahigh vacuum manipulator design that will integrate sample biasing and the potential for strain control across four beamlines at Diamond. The Structures and Surfaces Group includes four beamlines: 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 has continued to develop its strategy, outlining the facilities that we plan to offer 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, the discovery of novel quantum materials and catalytic/electrochemical systems under operando conditions are key drivers for these developments. Belowwe highlight some of the important developments on each instrument over the last year. Beamline I05: This world leading beamline delivered a suite of major upgrades including a new analyser on the high resolution end station, innovative capillary optics on the nanoARPES branch and a new high-flux grating to ensure that the ARPES experiments give as clear a view as possible of the sharp electronic bands in novel materials. The implementation of the ‘deflector mode’ allows angle resolved measurements to be recorded without having to physically move the sample, increasing the speed of data acquisition and maintaining the photon beam in a consistent position on the sample. For nanoARPES, excellent data quality is achieved through the ability to focus the beam onto high quality areas of the sample, which in many newly produced crystals may only be a few micrometres in size. Understanding how sample heterogeneity influences the electronic structure remains a very active focus of research on the beamline. The team on I05 is leading the development of a newmanipulator design to integrate electrical contacts that will enable direct biasing of the sample or control of a piezoelectric device to apply mechanical strain to a crystal. Strain device development is the subject of a joint appointment with the group of Clifford Hicks at the University of Birmingham, with miniaturisation of the device a key goal to enable rollout of these studies across multiple beamlines at Diamond. The scientific programme on the beamline continues to focus on novel new materials, including 2D materials and heterostructures, superconductors, magnetic systems and topologically non-trivial materials with some of the properties studied including charge density waves and the role of strain in adapting the electronic structure. Beamline I07: The team on the surface and interface diffraction beamline I07 has continued to focus on a number of key upgrades to enhance the capabilities. Continuous (fast) scanning of the diffractometer is now implemented for both experimental end-stations such that multi-axis motions enable scans along a specific trajectory in reciprocal space. Automated fast attenuators have been installed and integration with the detector and data acquisition software is currently being implemented. This will enable fast measurement of crystal truncation rods that cover many orders of magnitude changes in intensity. The Large Area Detector positioning system has been upgraded to extend the range of sample-detector distances that can be achieved, improving the grazing incidence small (wide) angle X-ray scattering (GIS(W)AXS) investigations. In addition, new implementations of Soller slits have been integrated to improve the signal to noise levels for several types of experiment. A long term ambitious plan continues to be discussed, to upgrade the optical layout of the beamline, switching from mirror focusing to making use of compound refractive lenses to provide additional tunability in the beam dimensions as well as a smaller ultimate spot size. A concurrent upgrade to the double crystal deflector (DCD) system would improve the ease of operation and enhance data quality for diffraction studies from liquid surfaces. The I07 team is also moving forward with improving the analysis software, in particular for visualisation of reciprocal space maps and reduction/extraction of crystal truncation rod data. The focus of research on the beamline continues to expand with new types of experiments implemented in the fields of electrochemistry, perovskite solar cells and molecular monolayers. Beamline B07: The second branch (B07B) of the VERSOX beamline expanded its number of user experiments in 2022, with the second end-station for UHV high-throughput X-ray photoelectron spectroscopy (XPS) studies, to enable chemical state analysis of many samples, having its first users. The initial end-station, developed in collaboration with Sven Schroeder’s group from the University of Leeds, for near edge X-ray absorption fine structure (NEXAFS) studies using soft X-rays to study materials such as organic molecules, battery materials, and catalysts has proven to be exceptionally productive. This branch has continued to improve through the integration of a vortex detector and very recently a UV-Vis spectrometer to correlate with the NEXAFS studies. The near ambient pressure XPS (NAP-XPS) system available on Branch C of the beamline continues to work well and has been enhanced by the implementation of a channel cut crystal monochromator that increases the flux at higher energies whilst also improving the energy resolution. Many of the studies on B07 focus on catalytic systems, electro- and photochemistry under operando conditions. The automated gas-rig and the close proximity of a state-of-the-art nanoparticle source (in collaboration with Richard Palmer from the University of Swansea) have added significant capabilities to the research portfolio at the beamline. Beamline I09: Beamline I09 has maintained a very active user programme whilst also working on a number of significant developments. The end station The I09 team and the soft X-ray end station. Surfaces and interfaces play an important role in broader research areas such as battery technology, photovoltaic structures, the discovery of novel quantummaterials and catalytic/electrochemical systems.