Associate Professor Josh Lipton-Duffin

  • Associate Professor Josh Lipton-Duffin

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Senior Research Officer, Associate Professor

PhD (Queen's University at Kingston)

I am a career surface scientist, interested in new materials and chemical reactions that occur on surfaces. Much of the very successful theories describing bulk crystalline materials is not applicable on surfaces, because most of our understanding of the solid state start from the assumption that crystal lattices extend very far in all spatial dimensions. Creating a surface throws a wrench into that very basic assumption, and quite often unusual phenomena will occur on surfaces that do not occur in the bulk. Studying surfaces is challenging: in air, a freshly cleaned or cleaved surface will typically be covered in a layer of nitrogen, oxygen or water molecules in a few nanoseconds! Thus, most of my work is done in ultrahigh vacuum, where surfaces remain clean and free of contaminants for hours (or longer); this affords opportunities for performing experiments free of the influence of contaminants or unwanted adsorbates. I spent a lot of time during my PhD (Queen's University, 2006) building bespoke equipment for surface science experiments. I have a passion for instrumentation as well as science, which serves well when a particular tool is unavailable and we are forced to improvise.

Projects (Chief investigator)

Projects

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Experience

I have nearly 20 years experience in surface science, including vacuum technologies, instrument design, spectroscopy and microscopy. My present research employs as many of these techniques as possible to uncover the structure-function relationship of novel materials; either common substances that are undergoing a "rediscovery", or bespoke materials designed from the ground up. During my MSc and PhD I designed and built an inverse photoemission spectrometer, which at the time represented the state of the art in the technique. Inverse photoemission is an exceptionally slow type of electronic density measurement, whereby electrons from a low-energy source are injected into the unoccupied states of a surface, and the light emitted during their capture is collected and analysed. Later I became an avid user of scanning tunnelling microscopy, a technique whereby a sharp probe is rastered across a surface to build up an image of the sample's topographic and electronic features. STM allows the user to "see" individual atoms and molecules, and is a particularly beguiling measurement, albeit sometimes tedious and not particularly fast compared to electron microscopies. I am also heavily reliant on photoelectron spectroscopy (PES), both in the laboratory (XPS/UPS) and using synchrotron light (SRPES). The synchrotron offers advantages in terms of tunability and flux, and permits experiments such as near-edge x-ray photoelectron spectroscopy (NEXAFS), which is a related technique for studying the electronic energy levels and orientation of adsorbed surface species.

Publications