IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Thursday Sessions
       Session SS1-ThP

Paper SS1-ThP9
Scanning Tunneling Microscopy Studies of the Growth and Morphology of Cu Clusters Deposited on TiO@sub 2@(110)

Thursday, November 1, 2001, 5:30 pm, Room 134/135

Session: Catalysis on Model Systems Poster Session
Presenter: J. Zhou, University of South Carolina
Authors: J. Zhou, University of South Carolina
J.E. Reddic, University of South Carolina
D.A. Chen, University of South Carolina
Correspondent: Click to Email
The growth of metals on oxide surfaces has become an important area due to the variety of applications involving metal-oxide interfaces. We have conducted scanning tunneling microscopy (STM) studies of Cu clusters grown on single-crystal TiO@sub 2@(110) (rutile) surfaces under ultrahigh vacuum conditions as a model for understanding the early stages of metal-on-oxide growth. Previous investigations of Cu deposited on TiO@sub 2@(110)-(1x1) have shown that the Cu clusters exhibit 'self-limiting' growth in the sense that with increasing coverage, the Cu cluster densities increase but the cluster sizes remain approximately constant. Our current studies of Cu grown on a partially reconstructed TiO@sub 2@(110)-(1x2) demonstrate that surface defects play an important role in determining the size and spatial distribution of the Cu clusters. Growth on the (1x2) surface is also 'self-limiting' and produces very uniform size distributions at all Cu coverages. However, the average cluster size at room temperature on the (1x2) surface (25Å diameter, 5Å height) is much smaller than on the (1x1) surface (~40Å diameter, 6-8Å height), and this difference is attributed to the decreased adatom mobility on the more defective (1x2) surface. Furthermore, the Cu clusters show no preference for residing at the titania step edges, which are the highest coordinate sites, even when the surface has been annealed to high temperatures (700-800 K) to increase the diffusion rate of the Cu adatoms. To further investigate this growth behavior, the initial stages of Cu cluster growth will be investigated by depositing Cu at low temperatures (25K-100 K) to prevent Cu adatom diffusion. The surface will then be heated to initiate adatom diffusion, and changes in the Cu clusters will be imaged by STM. We will also explore how the morphology of the Cu clusters is changed by oxidation at various temperatures. Both Cu deposition and oxidation studies can be performed during STM imaging.