Applied X-ray spectroscopy


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.

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2018 UROP students

This summer we have four great UROP (Undergraduate Research Opportunities Programme) students joining the group. All four are currently studying towards their BEng/MEng degrees in Materials Science and Engineering in the department. Amy Tall has been awarded an EPSRC Vacation Bursary, and Xiangqi Hu has been awarded an Imperial College UROP Bursary. Zhuocheng Xu’s project will be supported by Thermo Fisher Scientific.

Xiangqi Hu and Qiaochu Luo will be joining our CHIRP project team working on copper oxide nanostructure for glucose sensing, Amy Tall will be working on sol-gel synthesis for metal oxide thin films, and Zhuocheng Xu will be looking at radiation damage in catalyst systems.

If you want to know more about these great young scientist check out the group website.

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Our 2018 UROP students: Qiaochu Luo, Zhuocheng Xu, Xiangqi Hu, and Amy Tall (from left to right). 


Intermetallic PdIn Nanoparticle Catalysts

The final version of the PdIn intermetallic nanoparticles for CO2 to methanol hydrogenation paper is out in Applied Catalysis B: Environmental! Besides following changes in the sample characteristics using core level photoemission and correlating these with other characterisation methods, it also contains valence band spectra studying the change in electronic structure upon variation of the mixture of Pd and In in these intermetallic nanoparticles. The strong quenching of the density of states and change in structure of the valence states can be used to identify the sample chemistry in detail and can be directly linked to the behaviour of the catalysts.

This paper follows our previous work on Pd2Ga-based catalysts which we published earlier this year in ACS Catalysis.

PS: The paper is open access so what are you waiting for? Go read it now 🙂

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Characterisation LEGO

A few weeks back I found a great website by Boise State University which has LEGO instructions for a range of characterisation instruments. So naturally I had to try them out. I used Toy Pro to get all the necessary pieces and built the SEM and the XRD. I made a few custom adjustment particularly for the screens and control panels. I love the fact that the door opens on the XRD. Sadly, for now there aren’t any instructions for XPS – maybe I need to look into designing my own.

There might be a couple of safety issues in these labs (particularly the bunny next to the Erlenmeyer on the floor) but other than that I love the kits!


Polarisation dependent HAXPES – New paper out

A little while ago now Chemical Physics Letters published our paper on polarisation dependent hard X-ray photoelectron spectroscopy (HAXPES). This technique is still relatively new and not many publications are available. It shows particular potential for the identification of s states in valence band. The experiments were undertaken at the Taiwanese beamline BL12XU at SPring-8.

You can find the full article on the Chem. Phys. Lett. website

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New paper in press – Ga:In2O3

Finally, this beast of a paper has been accepted and is currently in press. You can already find the accepted manuscript on the Elsevier website. After a long review process I am very relieved that this is finally done. Now waiting for the proof and then the final version will hopefully be available soon. But with 19 figures and the current manuscript having a whopping 51 pages this might take a moment or two.

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PhD studentship available

Our group has a fully funded 3-year PhD studentship in “High-pressure Photoelectron Spectroscopy of Solar Water Splitting Materials” available to start in October 2015. It’s open to all UK/EU students who meet the EPSRC residency criteria.Payne Studentships Ad 2015

The full advert can be found on the group website http://payneresearch.org. For any further information please contact Dr David Payne (d.payne – at – imperial.ac.uk).


Pyrochlore Beauty

Since moving to Imperial in January I’ve gotten involved in a project on pyrochlores. To be more specific the “species” of interest is Pb2Ir2O6O’. Besides the fact that I seem to end up working with toxic chemicals wherever I go this is actually a structure of beauty. During my initial literature search I decided to play with the ONE reference structure on the ICSD and out came the picture below. It’s a view of the [111] face of said pyrochlore with the atom colours changed. I thought this is too pretty not to share. Now we’ll see how well the synthesis goes. Watch this space!

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