Functional Oxide Surfaces and Interfaces (FOXSI)

Metal oxides and, in particular, oxide surfaces and interfaces, are of paramount importance in many areas of chemistry and physics. Modern technologies utilize oxides in microelectronic circuits, sensors, piezoelectric devices, corrosion protection coatings, heterogeneous/environmental/photo-catalysis, power generation (fuel cells), etc. The atomic and electronic structure of oxide surfaces is often considerably different from simple truncations of the well-known bulk oxide structures. Especially when the thickness of oxide layers reaches the sub-10nm range, the films generally no longer exhibit bulk characteristics, resulting in modified physical, chemical, electrochemical, electrical, magnetical, etc. properties. Modified oxides (mixed, doped, multicomponent oxides; metal contacts) play an even bigger role in technology but a fundamental understanding of the parameters governing their properties is still lacking. When oxides are employed in technological processes and act as "functional oxides", they are exposed to a gaseous or liquid environment that further modifies their structure and thus properties. Future advances in oxide-based technology will rely on a fundamental understanding of the surface chemistry and physics of the involved materials and on identifying structure-function relationships. This requires an array of methodologies and techniques that can only be provided by concerted efforts of research groups specialized in oxide synthesis, and in experimental and theoretical characterization. The proposed SFB brings together 11 research groups active in studying functioning oxide surfaces and interfaces, with expertise in surface/interface chemistry and physics, fuel cell technology and microelectronics. By pooling groups that usually belong to separate scientific communities, a full scale investigation of processes on well-defined oxides becomes feasible, touching the frontiers of research on complex materials. The "Core Topics" are: i) Structure of functional oxide surfaces and interfaces; ii) Gas-oxide interactions; iii) Functional oxides under working conditions. The "Core Materials" (pure and Y-modified ZrO2, CeO2, perovskites, oxide-metal interfaces), which are important in catalysis, fuel cell technology and microelectronics, will be prepared by various physical (PVD, MBE, ALD, PLD, lithography) and chemical methods. The surface, interface and bulk structures of the involved materials will be investigated by a variety of state-of-the-art microscopic and spectroscopic methods, including STM, AFM, TEM/SEM, PEEM/FIM, SXRD, XPS, AES, LEIS, PM-IRAS, FTIR, SFG, TPD, TOF-SIMS, UV-Vis, PL, impedance, C-V/I-V, DFT etc. A number of these methods is particularly suited to monitor oxide materials under operating conditions. The concerted efforts of the SFB will allow evaluating the growth and physico-chemical properties of (complex) oxides, providing detailed insight into catalytic properties, oxygen activation kinetics on perovskites relevant for fuel cells, and into the electrical properties of oxides in microelectronic devices. The knowledge gained on oxide functionality will also have impact on related fields such as sensors, corrosion, inorganic structure chemistry, and others.