The pace of modern technological development - from microelectronics to catalysts, to coatings - is driven by fundamental breakthroughs in fabricating novel nano-structured materials. Such materials often promise unique or enhanced physical characteristics, such as strong magnetisation or unusual reactivity. These characteristics will derive from, but can also be compromised by, subtle, atomic-scale structural variations. In each case, nano-resolved characterization is essential and full understanding of a material demands multiple state-of-the-art experimental probes. The probes used in my research include beams of electrons, atoms, ions, and photons, as well as physical devices such as the tip of an atomic force microscope. Each probe has its advantages and its limitations and the best studies of nanostructured material combine the results from several probes in order to develop a complete description.

A selection of my recent projects is given below. The uppermost projects derive from my time in Glasgow, whilst some of those below are based on collaboration with colleagues in Cambridge, where more information can be found.

• Pulsed Laser Deposition
• Nanoparticle characterization
• Structural characterization of nanomaterials
• Analytical electron microscopy
• X-ray spectroscopy
• Atom interferometry
• Development of Scanning Helium Microscopy
• Studies of thin film growth
• Medium energy ion scattering
• Gas detection via field ionisation from carbon nanotubes

Gas detection via field ionisation from carbon nanotubes

Whilst inert helium has many advantages as a probe of surface structure, it's inert, uncharged character also causes problems for detection. In particular, there is no analogue of the fluorescent screen often used in electron beam techniques (e.g. electron microscopy) and most helium diffractometers use a modified mass spectrometer for beam detection. The first and limiting stage of mass spectrometry is in ionising the uncharged helium, where efficiencies of 10 per million are typical - i.e. for every million He atoms passing through a conventional detector, only around 10 are actually detected! In collaboration with Cambridge University's Department of Engineering we developed a prototype detector using carbon nanotubes. This novel detector was based on a 'forest' of multi-walled CNTs grown onto a steel substrate. The substrate was held at high positive voltage such that nearby gas species were 'field ionised' within the extreme electric fields surrounding each nanotube tip. In theory, ionisation efficiencies can be improved by several orders of magnitude with the technique. Results are illustrated in the sketch above, which shows the ion current from a positively-biased CNT-coated sample in ultra high vacuum and in the presence of helium gas. The prototype demonstrated the viability of our novel approach and has attracted substantial interest worldwide. It was also highlighted by the Institute of Physics' online news journal, nanotechweb.org. Publications: 7.