Applied X-ray spectroscopy

Looking for cross sections?

Over the past few weeks the group set off on a joint adventure to digitise the famous photoionisation cross section dataset from Yeh and Lindau. Initally published in 1985 in Atomic Data and Nuclear Data Tables under the riveting title Atomic Subshell Photoioization Cross Sections and Asymmetry Parameters, this work has become one of the staple references for practitioners of spectroscopy far and wide. The only slight complication: the available online version is on the blurrier end of digitised PDF documents and it’s hard to search and copy out data points by hand, when you need them (automatic digitisation software doesn’t work very well due to the pixelation of the PDF).

This is why the group, under the expert leadership and organisational talent of Curran Kalha, embarked on a Covid-19 lock down activity of going through the tables of 103 elements, entering them one by one into a rather large excel file and then cross checking all entries. After an encouraging email exchange with Prof. Lindau we are now able to share the files with everyone who can make use of them. Go to the research subsection of our website to download the dataset. You can also find the dataset on figshare. Feel free to share widely and we hope it will help many of you!

A big THANK YOU to Curran, Nathalie, Carolina, Ebru, Yun and Jiebin who all contributed to this group effort!

PS: Our main motivation to do this was to now use the dataset to incorporate it into the Galore software package. This is happening as we speak so for all you pDOS lovers out there you should soon be able to use the full set of Yeh/Lindau cross sections in Galore.

PhD studentship available

We currently have a fully-funded PhD studentship available in the group.

The project is on metal oxide thin films for electronic devices to start in September 2020.

Metal oxides are one of the top candidates to help us move from the silicon age into a new era of more powerful, energy efficient, and flexible electronics. They show the widest range of physical characteristics of any material family and in devices are often used in the form of thin films. High-quality oxide films are necessary to develop advanced device generations and in this project you will explore wet chemistry processes, like sol-gel synthesis, to prepare such films. The sol-gel process is fast, inexpensive, technologically simple, and can be executed at low temperatures enabling the use of flexible substrates. Through adjustment of the process parameters, including precursor type and concentration, use of stabilisers and catalysts, reaction temperature, and many more, the film characteristics can be engineered and optimised. This approach allows the comparatively easy fabrication of high-quality new oxide thin film materials, which can subsequently be tested for their fundamental chemical and physical characteristics. You will investigate structure, electronic structure, and chemical state of the thin films using a combination of characterisation techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM) and atomic force microscopy (AFM). The detailed knowledge of the characteristics and behaviour of new materials then enables their implementation in applications, such as new generations of electronic and optical devices. This project will combine elements of thin film deposition, solid state chemistry, and electronic devices. It is best suited for students with a keen interest in multidisciplinary work at the interface of fundamental materials chemistry and device applications.

Interested candidates should initially contact the supervisor DI Dr Anna Regoutz () with a degree transcript and a motivation letter expressing interest in this project. Informal inquiries are encouraged. Suitable candidates will be required to complete an electronic application form at Any admissions queries should be directed to Dr Jadranka Butorac ().

Applications will be accepted until 30th April 2020 but the position will be filled as soon as a suitable candidate has been identified.

Welcome Curran!


Curran Kalha joined the group last week and will be undertaking a PhD in the X-ray spectroscopy of multilayer structures particularly concerning materials for power electronics. He is starting his PhD with his first beamtime at beamline I09 at Diamond Light Source studying metallisation systems for power electronics this week. His PhD project will focus on developing and establishing measurement protocols for these important multilayer systems and he will make extensive use of XPS, HAXPES, AR-HAXPES, and XAS.

Curran graduated with an Integrated Master’s degree in Chemical and Process Engineering from the University of Leeds in 2019. During his third year of study, Curran worked on a project in association with Proctorand Gamble, to design a new processing route for the manufacture of high bulkdensity detergent powder. During this project, Curran gained experience in the field of powder research, both theoretically and experimentally. This experience led him to an industrial placement at the Ministry of Defence, wherehe switched working with detergent powder for energetic formulations. Here he developed the process route and characterisation protocol for a new PBX formulation. Curran’s work was selected for presentation at the 49th International Annual Conference of the Fraunhofer ICT on Energetic Materials. After completing the year placement, Curran developed an interest in developing and characterising new materials. Upon returning to university, Curran decided to focus his master’s research on investigating the synthesis of garnet oxide materials for all-solid-state Li-ion batteries using various sol-gel processing techniques.

Nathalie Fernando presents poster at MC14

Nathalie Fernando, PhD student in the group who is part of the CDT in Advanced Materials Characterisation, presented her first poster at MC14 (14th International conference on materials chemistry) in Birmingham this week.

Nathalie is working on photon-matter interactions and in particular the effects of X-rays on the structural and electronic structure of catalyst materials. She combines X-ray spectroscopy and X-ray diffraction, and compares results to DFT outputs, to gain an in-depth understanding of the processes involved. Nathalie is supervised by Anna and co-supervised by Rob Palgrave (UCL) and Andrew Cairns (ICL). The work includes a number of awesome collaborators, including Claire Murray (Diamond Light Source), Amber Thompson (University of Oxford), and David Scanlon (UCL).


It’s all about osmium (and parties)


OsO2 is one of those forgotten and ingnored binary oxides in the periodic table. The main reason for this lack of interest is it’s unwanted tendency to form highly toxic and volatile OsO4, which makes the synthesis and characterisation of samples somewhat challenging. It is fair to say that to publish this paper a number of H&S officers had to be convinced that we would not kill an entire beamline team with an ill adviced heating or sputtering attempt.

Although studying OsO2 has it’s challenges, there are a number of clear motivations for why we want to know more about it’s characteristics, beyond sheer scientific curiosity. OsO2 is a transition metal dioxide and it is part of an illustrious group of rutile metallic oxides, including IrO2, RuO2, PtO2, TcO2, and ReO2. It is also the parent oxide of the family of osmates, which similar to their cousins the iridates, are starting to show a range of interesting physics, including metal-insulator transitions and exotic magnetic behaviour.

In this work we used a combination of theory and experiment to gain some understanding of the electronic structure using hard and soft X-ray spectroscopy and density functional and many-body perturbation theory. Beyond providing an understanding of all occupied states of OsO2 we also identified a low-energy plasmon within the valence states. And if you ever wanted to see an intimidating peak fit look no further than the Os 4f/5p core level.

If you’d like to read more about this work, check out the full manuscript in Physical Review Materials.

Now at this point you might rightly ask what all of this has to do with parties. Well, this paper presents a personal milestone for Anna, as it is her 50th peer-reviewed manuscript to be published.

Interfaces in high power electronics


Silicon carbide (SiC) is one of the candidates for future metal-oxide-semiconductor (MOS) devices, in particular for high power applications. One main reason for the interest in SiC is that it comes with its own native dielectric, silicon dioxide (SiO2). However, devices made from SiC still struggle to achieve the high quality SiC/SiO2 interfaces necessary for optimum device performance and stability.

We have worked together with colleagues from Infineon Technologies Austria and KAI to explore this buried interface using X-ray photoelectron spectroscopy (XPS) to systematically study the local elemental distributions and chemical environment. We compared a range of device stacks after varying nitridation treatments, which can help lower interface defects and improve electrical device behaviour.

If you want to know more about this exciting exploration of an interface using X-ray spectroscopy head to the Journal of Materials Chemistry C to check out our recent paper. It was published as part of the 2018 Journal of Materials Chemistry C Emerging Investigators themed collection. Do check out the collection as it contains a number of great papers from exciting young materials chemists.

MSc and UROP student success

This summer the group hosted two MSc students, Shijia Liu and Ayse Ay, who worked on CuO nanostructures for glucose sensors, and four UROP students, Amy Tall, Zhuocheng Xu, Xiangqi Hu and Qiaochu Luo, who worked on transparent conducting oxides, radiation damage in amino acids, and copper oxide glucose sensors.

All of them contributed a great deal to the group. Excellent science happened, lots of fun was had (from nanogranola to nanocornflakes), and we conquered many realistic labexperiences (and struggles). It was such a pleasure to work with all of these excellent Materials students! We can’t wait to see where they go next.


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Group lunch: Amy Tall, Zhuocheng Xu, Xiangqi Hu, Shijia Lia, Ayse Ay, Qiaochu Luo, Anna Regoutz.

MSc Advanced Materials 2017-18

MSc Class 2017-18, including Ayse Ay (1st row, 4th from left) and Shijia Liu (1st row 4th from right) who worked on projects in the group (photo courtesy of Raj Adcock).

Hard X-ray Photoelectron Spectroscopy in the Laboratory

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Hard X-ray Photoelectron Spectroscopy (HAXPES) is becoming more and more popular as a characterisation technique for the bulk of materials as well as buried layers and interfaces. To date, most experiments are hosted as beamlines on synchrotrons and only a small number of such systems is available worldwide.

In order to open up the technique to a wider user base, new laboratory-based systems are being developed. Together with Scienta Omicron we have worked on such a system based on a monochromated, liquid Gallium X-ray source delivering a microfocused X-ray beam. This in combination with a state-of-the-art photoelectron analyser enables high resolution measurements of a range of samples.

If you want to know more about this exciting prototype and see some spectra collected on reference and applied materials, check out our paper in Review of Scientific Instruments. The paper is open access so freely available to everyone.

Galore – when experiment and theory come (closer) together

Bringing experiment and theory together can sometimes be a bit of a challenge. Lead by excellent colleagues at UCL, Adam Jackson, Alex Ganose, and David Scanlon, we have bridged one of the many exisiting gaps between the two.

Photoelectron spectroscopy generates valence band spectra, which are directly related to the electronic density of states of a material. Sounds simple, but although the density of states can nowadays be easily calculated using ab initio methods, a number of adjuments are necessary to make the pure theoretical results comparable to the measured spectra. The most crucial one is to apply weightings to the different orbitals based on the photoionisation cross sections. This is usually combined with the application of some level of Gaussian and/or Lorentzian broadening.

Galore is a software package that automates the corrections to the calculated density of states, which previously had to be done in often rather laberous ways. Galore is available on GitHub and any feedback is very welcome! We’ve also published a paper in The Journal of Open Source Software, where you can find more background and details about Galore.