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David Andrew Duncan

Associate Professor, Faculty of Science

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Biography

David Andrew Duncan received a M.Sci in Chemical Physics from the University of Glasgow in 2008. He obtained his Ph.D. in Physics, under the supervision of Prof. D. Phil Woodruff, from the University of Warwick in 2012. His Ph.D. thesis, Adsorbate structure determination using energy scanned photoelectron diffraction was awarded the IOP's Thin Film and Surfaces Thesis Prize, the Woodruff Thesis Prize in the same year. After a brief postdoctoral appointment at Diamond Light Source, he began a postdoctoral fellowship at the Technical University of Munich, funded by an Alexander von Humboldt fellowship and, latterly, a Marie-Curie intra-European fellowship. In 2015 he was appointed as a beam line scientist, latterly senior beam line scientist (2018) at Diamond Light Source. In 2024 he moved to the University of Nottingham, where he is currently Associate Professor of Physical Chemistry in the School of Chemistry. His current research is based on quantitative structure determination of adsorbates on surfaces, with a focus in 2D materials and single atom catalysts.

Expertise Summary

Structure of single metal atoms on surfaces

Image Structure of single metal atoms on surfaces

Single atom catalysis is a promising method for, not only maximising the utilisation of often precious catalytically active material (e.g. Pt, Rh, Pd), but could also open up brand new avenues of chemistry. One particular single atom catalytic candidate is single adatoms on the (001) surface of magnetite. Since 2017 we have been studying the adsorption of metal adatoms on this surface, specifically confirming quantitatively, for the first time, the adsorption site of these adatoms bridging two surface oxygen atoms using normal incidence X-ray standing waves. We are currently in the process of studying the interaction of these adatoms, and this surface in general, with molecular adsorbates.

Controlled fabrication of defects in graphene-like films

Over the last thirty years we have improved our capability to fabricate ideal graphene over macroscopic scales, with recent reports of single domain growth up to 1 meter. However, graphene itself is chemically comparatively noble and has no band gap, limiting its scope of applications for catalytic, gas sensor and electronic applications. Inducing defects into graphene is one way to make it more chemically reactive for catalytic and gas sensor applications or to form a material with a band gap for electronic applications. However, many methods for creating these defects tend to be top down and result in poor controllability and reproducibility, as well as creating many different kinds of defects. Since 2021 we have been developing methods for chemical vapour deposition based growth of defective graphene-like films, where the type of defect created in the resulting film is chosen by careful selection of the precursor used. We have had significant success in inducing topological defects (defects where the C atoms are no longer in 6 membered rings), and are currently in the process of developing methods for growing graphene with heteroatom defects instead.

Surface functionalisation by molecular adsorption

Image Surface functionalisation by molecular adsorption

While much of the electronics industry is dominated by inorganic materials (e.g. silicon), molecular electronics, due to the immense breadth of carbon chemistry, have a promise to provide a range of functionality that is simply inconcievable with inorganic materials. Understanding how organic matter interacts with inorganic support materials on a fundamental level is key to rational development of future devices. The high precision quantitative information obtained from techniques like X-ray standing waves, photoelectron diffraction and surface X-ray diffraction can provide powerful benchmarking against theoretical calculations and can yield fundamental insight into the organic / inorganic interface.

Quantitative structure determination

X-ray standing waves (XSW), unique amongst the surface structure determination techniques, can be analysed by direct methods (not requiring lengthy trial and error process, like in quantitative low energy electron diffraction (LEED-IV), photoelectron diffraction and surface X-ray diffraction (SXRD)). Thus, the structural parameters obtained by XSW are a certain representation of the structure of the system you actually measured, it is not imagination limited where you must first imagine what the correct structure is, before you can say anything meaningful about it. Furthermore XSW can be acquired by monitoring photoelectron yield, which provides a chemical sensitivity to the technique. One can differentiate directly the structure of, for example C atoms bound to only other C atoms, or C atoms bound to O atoms, or even C atoms part of an alcohol group, or part of a carboxylate group. Thus, XSW is a powerful technique for studying the adsorption structure of molecules on surfaces, of 2D films on their growth substrates and of metal adatoms adsorbed on surfaces. However, a key cavaet of XSW is that it requires a nearly perfect crystalline substrate supporting the adsorbed material, from which one generates the X-ray standing wave. Thus it cannot be performed from powders, or foils and has specifically limited applications in layered and thin film materials.

Energy scanned photoelectron diffraction (PhD), while imagination limited, is a powerful technique for probing the local environment around an atom. Unlike, for example, LEED-IV or SXRD, it does not require that the adsorbed material is itself crystalline (i.e. has a clear well defined 2D repeating unit cell), but solely requires that the local environment around the probed atom is well defined (e.g. it is uniformly in a 3 fold coordination site, with its nearest neighbour atoms). As it is a photoelectron based technique, it yields chemical sensitivity allowing the structure of species in different chemical states (e.g. O atoms in molecular water, in a surface hydroxyl group or the bulk O atoms of an oxide sample) to be individually analysed.

Selected Publications

  • KLEIN, BENEDIKT P, STOODLEY, MATTHEW A, MORGAN, DYLAN B, ROCHFORD, LUKE A, WILLIAMS, LEON BS, RYAN, PAUL TP, SATTLER, LARS, WEBER, SEBASTIAN M, HILT, GERHARD and LIDDY, THOMAS J, 2024. Probing the role of surface termination in the adsorption of azupyrene on copper: Nanoscale Nanoscale. 16(11), 5802-5812

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