Diamond Annual Review 2019/20

28 29 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 1 9 / 2 0 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 1 9 / 2 0 work independently, this will bring additional capability and supplement the techniques offered by the group. The near-ambient pressure XPS system available on Branch C of the beamline continues to work well with the first user publications coming out at the end of 2019. The possibility of measuring XPS spectra up to pressures of 50 mbar is opening up new avenues of research, particularly with the focus on understanding catalytic processes in greater detail. In addition, the relatively wide photon energy range (180 eV to 2800 eV) enables experiments which are not possible at many other beamlines (e.g. Boron, Sulphur K-edge NEXAFS). Different end stations are available depending on the requirements of the experiment.The gas handling capability of the beamline is being improved through the installation of an automated gas delivery system to enable accurate control of the sample environment in terms of gas composition and pressure. The beamline team have ambitious plans to expand the facilities offered to enhance studies on solid-liquid interfaces and nano-clustered samples. Beamline I09 has had several years of major upgrades whilst maintaining an exceptionally active user programme.This year saw the hard X-ray (HAXPES) system move to its final location on the hard X-ray branch, and with-beam commissioning is underway whilst the next large end station for soft X-ray ARPES (also known as a momentum microscope) is expected to be delivered this year. The unique design of the beamline means that the hard and soft branches can operate independently or be combined into end station 2, where the majority of the work has been undertaken since the beamline opened to users. Smaller scale upgrades have continued to add to the capabilities of the beamline, notably, a new manipulator that enables sample biasing, cooling and heating whilst still allowing sample transfer has been built and installed in end station 2. Future plans include replacing the simple (three fixed energy) monochromator with a fully tuneable version to enhance the HAXPES studies and an upgraded plane grating monochromator to improve the resolving power (energy resolution) of the soft X-ray branch. The group are aiming to enhance the associated infrastructure available for surface science research, including the design of a new offline ultrahigh vacuum system to characterise samples that could then be studied on the beamlines. This will position Diamond to be able to rapidly study new samples and enhance the link between laboratory-based and synchrotron-based studies. We aim for this capability to be at the core of many of the joint PhD studentships that we support. The proposal was well received by the SAC and design work will start on the system in 2020. The range of science undertaken at the beamlines continues to be a combination of detailed surface science characterisation through to the application of the methods to novel samples, as outlined in the contributions from a selection of our users. There is also a shift towards many more multi- modal experiments that make use of several techniques to answer a scientific question. This is shown in the science contribution from Rosa Arrigo who has used B07, together with electron microscopy, diffraction and spectroscopy to understand the nature of the preferential formation of one chiral enantiomer by catalysis using nanoparticles. The report by the group of Emmanouil Dimakis highlighting work on I07 to understand the in-plane strain in core- shell nanowires of GaAs/InGaAs also combines the diffraction measurements with electron microscopy and compositional information. The application of the techniques to different types of samples or processes continues to grow as exemplified in the contribution by Louis Piper who studied samples relevant to the production of hydrogen via photocatalysis of water for clean energy through optimisation of the sample composition. Fundamental scientific studies form a large part of our portfolio and particularly noteworthy this year has been the discovery of a Weyl fermion in a magnetic compound by the group of Yulin Chen. The angle resolved photoemission data recorded on beamline I05 displayed the key characteristics predicted by the theoretical calculations and details of the dispersion of the features were also measured, adding to the evidence of this quasiparticle. The members of the Structures and Surfaces Group are committed to continuing to offer 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 and technique development is key to our success. Please contact us if you would 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 he Structures and Surfaces Group comprises four beamlines: I05 (Angle Resolved Photoemission 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). These offer a variety of techniques to examine the atomic-scale structure, chemical nature and electronic states at buried interfaces or the surfaces of materials, and in novel quantum materials. Developments are increasingly enabling the studies to be performed under operando conditions or during sample biasing, extending the range of scientific questions that can be explored. The group is continuing to expand the capabilities of the beamlines whilst also taking a strategic view for the future, through the development of a long-term roadmap of major upgrades, additional technique developments and potential new beamlines based on the workshop held last year. The Diamond-II science case highlighted, in particular, the important role that surfaces and interfaces play in broader research areas such as battery technology, photovoltaic structures, electronic devices (e.g. transistors) and catalytic/electrochemical systems under operando conditions. Expanding the techniques to these communities remains a key aim for the group. Beamline I05 successfully completed its first beamline review by an expert panel that reports to the Scientific Advisory Committee (SAC). The quality of the research output, the impact (quality of the papers and citations generated) and the expertise and support of the beamline team were all highlighted as helping to make I05 a world-leading ARPES facility. The high- resolution branch is completing its upgrades to the gratings and electron energy analyser, whilst the NanoARPES end station will deliver improved flux through the incorporation of a capillary mirror. The team welcomed Matthew Watson, who had previously been a post-doctoral researcher at Diamond, back to the beamline as a beamline scientist. The group have ambitious plans for developing photoelectron spectroscopy at Diamond to complement the high- resolution facilities available on I05, the arrival of a soft X-ray ARPES system (momentummicroscope) this year on I09, the hard X-ray (HAXPES) station also on I09 and the near ambient pressure (NAP-XPS) capability on B07. The surface and interface diffraction facilities on beamline I07 are being upgraded to enhance the capabilities. This includes integrating continuous scanning of the diffractometer to improve the data collection efficiency and developing automated, fast attenuators to enable fast measurement of X-ray reflectivity and crystal truncation rods that cover many orders of magnitude changes in intensity. A new Excalibur detector is also being commissioned to replace the Pilatus P100K detectors mounted in the first experimental hutch. The diffractometer is being adapted to increase the range of one of the circles whilst a new hexapod will increase the reliability and speed of experiments and allow the use of heavier sample environments (up to 200 kg). There is a long term plan to revisit the optics layout of the beamline with the ambition of reducing the beam size and increasing the flux at the sample.This may include use of amultilayer monochromator, newmirrors or compound refractive lenses and upgraded double crystal deflector system for liquids studies and improved beam intensity monitoring. This year, the second branch of beamline B07 (VERSOX) will open to users, initially enabling Near Edge X-ray Absorption Fine Structure (NEXAFS) studies using soft X-rays to study processes such as molecular adsorption or catalysis.This will be complemented by a high throughput XPS/NEXAFS system that will allow chemical state analysis of many samples where the tuneable photon energy from the synchrotron source can be utilised to measure and/or enhance the signal from low atomic number elements. As the two branchlines