AVS 56th International Symposium & Exhibition
    Surface Science Tuesday Sessions
       Session SS2-TuM

Paper SS2-TuM2
Surface-catalyzed O2 Adsorption on Quantum Thin Films

Tuesday, November 10, 2009, 8:20 am, Room N

Session: Reactions on Metals and Bimetallics
Presenter: J. Kim, The University of Texas, Austin
Authors: J. Kim, The University of Texas, Austin
A. Khajetoorians, The University of Texas, Austin
W.G. Zhu, Oak Ridge National Laboratory
Z.Y. Zhang, Oak Ridge National Laboratory
C.K. Shih, The University of Texas, Austin
Correspondent: Click to Email
Pure crystalline Pb is well known to be inert with respect to oxygen gas. By using scanning tunneling microscopy we demonstrate that the oxygen adsorption on Pb films is greatly increased by Cs adsorbates acting as catalysts. Our previous studies show that Cs atoms can be easily incorporated into the surface layer of thin Pb films through a substitutional process when they are evaporated at low temperature (100 – 120 K). In addition, this Cs-Pb surface alloying process works cooperatively with the quantum size effect, leading to formation of nano-islands. This study explores the effect of the surface alloying on the oxidation. With only a minute concentration of Cs (0.004 ML coverage), we found a great enhancement of surface oxidation rates. Theoretical DFT calculations have revealed that the oxygen adsorption energy is greatly enhanced at the Cs substitutional sites. Subsequent oxygen exposures lead to great enhancement of oxidation which can be identified as PbO. Furthermore, we have explored the effect of temperature on the formation of Cs-Pb alloy and its consequences for the oxidation of Pb.