Our work on how structural differences in Ga₂O₃ polymorphs can be detected in X-ray photoelectron spectroscopy and what differences exist in the electronic structure of the different polymorphs has just been published in Chemistry of Materials. You can also find the paper on arxiv.

This one has been in our paper pipeline for a while – not because it’s not interesting, but because this was a rather complicated and multifaceted story to pull together. Taking a quick look at the author list (a whopping 24 co-authors) you can tell that we needed to involve several growth, characterisation, and theory experts to be able to systematically explore and understand the scientific questions we set out to answer. This work is a great example of how important collaboration and involvement of groups across different disciplines is. We are fortunate to be able to work with such a great team!

At the heart of the work are high quality single crystal and epitaxial thin film samples of alpha-, beta- and epsilon-Ga₂O₃, that we explored using a number of advanced characterisation techniques. In particular, we combined SXPS and HAXPES to compare surface and bulk spectra, from shallow to deep core levels and valence states. Combined with XAS we were able to provide an overview of both occupied and unoccupied states in the polymorphs. What is particularly exciting from a spectroscopy point of view is that we were able to explain the core level line shapes using high-level theory and to clearly show the influence of the local coordination of Ga atoms on the spectroscopic results.