Investigating Solid Surfaces at the Atomic Scale
Ulrike Diebold (UD) is an experimental surface scientist with a research focus on metal oxides. In her research lab she uses Scanning Tunnelling Microscopy (STM), in combination with surface spectroscopic and diffraction techniques to unravel the atomic-scale geometry, electronic structure, and reactivity of surfaces at the atomic scale. Her ultrahigh vacuum (UHV) systems are also equipped with deposition sources and for molecular-beam epitaxy (MBE), and a PLD system with in-situ RHEED for Laser-MBE is currently being implemented in one of her surface analysis setups.
UD’s research program predominantly deals with metal oxides. After all, most metals are oxidized in the ambient atmosphere, so it is, in fact, the oxide surface that deserves most attention. In addition, metal oxides exhibit an extremely rich variety of chemical and physical properties. While some metal oxides are chemically so inert that they are used as corrosion protection layers, others prove to be active and selective catalysts. The best electrical insulators, yet also the most-promising high temperature superconductors belong to the class of metal oxides. Due to this high tunability of their physico-chemical properties, metal oxides are used in many different technical areas – as gas sensors, catalysts, solar cells, batteries, opto-electronic devices, etc. In virtually all applications the surfaces of metal oxides play a major, and often the dominant role. Hence a more complete understanding of the surface of a metal oxide surface is key to understanding, and ultimately, improving device performance.
STM allows investigating processes at surfaces in a direct manner, and on a molecule-by-molecule basis. Many processes at metal oxide surfaces are defect-mediated, which makes imaging at the atomic scale particularly important, and a judicious design of ordered defect arrays helps with devising appropriate model systems. Adsorption and diffusion processes, both at the surface and involving subsurface regions, are important to understand dynamic mechanisms at surfaces. So far UD has mostly concentrated on semiconducting binary metal oxides such as TiO2, SnO2, ZnO, or Fe3O4. With epitaxial thin film growth, the range of samples can be extended to materials that are not easily available in single-crystalline form, such as Sn-doped In2O3 and, in the future, perovskite materials.