MSE Seminar Series: Michael J. Bedzyk
Friday, April 6, 2012
1:00 p.m.-2:00 p.m.
Room 2110 Chemical and Nuclear Engineering Bldg.
301 405 5240
X-ray Atomic-Scale Structural Studies of Interfaces with Chemical-State Sensitivity
Michael J. Bedzyk
Professor and Chair
Materials Science and Engineering
Interfacial science by its very nature brings together diverse interests in areas such as: electronic materials, oxide film growth, nano-science, biomembranes, geochemistry, surface physics, catalysis, and electrical-energy storage. Sophisticated in situ X-ray methods are now being developed to understand the assembly of atoms, molecules and supported nanoparticles at well-defined interfaces in complex environments. The talk will introduce the use of synchrotron X-ray methods for atomic-scale studies of interfaces. Examples will include the use of X-ray reflectivity (XRR), X-ray standing waves (XSW) and X-ray photoelectron spectroscopy (XPS) for studying interfaces formed by the growth of graphene on silicon-carbide and metallic monolayers on oxide single crystal surfaces. For epitaxial graphene grown on the Si-face of SiC(0001), XPS shows a number of distinct chemically-shifted C 1s peaks that when monitored individually under the XSW condition are shown to correspond to C atoms located in different sites including the controversial interface layer that lies between the substrate surface and first graphene layer. For the case of an oxide supported monolayer catalyst, VOX on α-TiO2(110), we are able to correlate the redox-induced interfacial chemical-state changes of the V ions (observed by XPS) with their atomic-scale structural changes (observed by XSW 3D atomic imaging). In both cases the chemically-specific structural measurements are well-suited for testing modeled theoretical predictions and for complimenting local-probe imaging methods. The measurements were made at the Advanced Photon Source and the European Synchrotron Radiation Facility.