AVS 52nd International Symposium
    Surface Science Monday Sessions
       Session SS2-MoM

Paper SS2-MoM8
Imaging of Atoms on Oxide Surfaces by X-ray Standing Wave Fourier Inversion

Monday, October 31, 2005, 10:40 am, Room 203

Session: Oxide Surface Structure and Characterization
Presenter: C.-Y. Kim, Northwestern University
Authors: C.-Y. Kim, Northwestern University
J.W. Elam, Argonne National Laboratory
D. Goswami, Northwestern University
M.J. Bedzyk, Northwestern University
P.C. Stair, Northwestern University
S Christensen, Northwestern University
M.C. Hersam, Northwestern University
Correspondent: Click to Email
Supported metal oxides are among the most important of catalytic materials systems. However, there is a lack of experimental atomic-scale structural information for describing the relevant interfaces. We combine atomic layer deposition (ALD) and x-ray standing wave (XSW) atomic-imaging to address this challenge. As a first case, we determine the precise registry of W atoms on a rutile TiO2(110) surface. XSW results show that tungsten has an average adsorption height of 3.48 @Ao@. above the Ti-O plane. The direct-space image reveals that W occupies the Ti-site that would be occupied by Ti if the bulk structure were extended above surface. The tungsten atoms are vertically shifted upward from the ideal Ti-site location by +0.23 @Ao@. We speculate that the sacrificial role of Si2H6 in removing surface species may apply to the TiO2 substrate in addition to the W ALD film. This is the first atomic structure determination of a supported catalytic phase under ambient conditions. The results suggest that supported metal cations locate as if they were the next layer in the bulk structure. The ALD method for supported catalyst material preparation provides a bridge over the "materials preparation gap" that typically separates practical, high-surface-area and single crystal model catalytic materials.