David's research to date has focused on the investigation of the electronic structure of functional oxide materials, particularly the oxides of the post-transition metals. The research focus of the group is shown below: A range of spectroscopic techniques have been employed including soft and hard x-ray photoelectron spectroscopy (XPS and HAXPES), x-ray emission and absorption (XES and XAS). These experiments have been performed at a number of national and international synchrotron radiation facilities including the ALS (Berkeley, U.S.A.), Diamond (Harwell, U.K.), Elettra (Trieste, Italy), ESRF (Grenoble, France), Max-Lab (Lund, Sweden), NSLS (Brookhaven, U.S.A.). High-resolution XPS has also been performed at NCESS (Daresbury, U.K.). The materials under investigation have been synthesized using different methods. Single crystalline thin films are produced using oxygen plasma assisted beam epitaxy (OPABE) in ultra-high vacuum (UHV) conditions. X-ray diffraction (XRD) (synchrotron- and lab-based), atomic force microscopy (AFM), high- resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) are all used to characterize the films. Underpinning the work done in UHV, more conventional methods of solid state synthesis are undertaken to produce ceramic samples.