AVS 52nd International Symposium
    Applied Surface Science Thursday Sessions
       Session AS+TF-ThA

Paper AS+TF-ThA4
Thin Films of Fe on Pt(111) : Alloy Formation

Thursday, November 3, 2005, 3:00 pm, Room 206

Session: Thin Film Characterization II
Presenter: M. Yoshimura, Toyota Technological Institute, Japan
Authors: M. Yoshimura, Toyota Technological Institute, Japan
S. Komaru, Toyota Technological Institute, Japan
K. Ueda, Toyota Technological Institute, Japan
Correspondent: Click to Email
Addition of transitional metals to Pt catalysts has been known to improve catalytic efficiency. Pt-Fe bimetallic catalysts attract attention in industrially important fields such as polymer electrolyte fuel cell (PEFC).@footnote 1@ Modification of geometrical and electronic structure of Pt surface would be responsible for the improved efficiency. Recently, Jerdev et al. examined Fe-Pt alloying processes by XPS and LEED.@footnote 2@ They found that heating thick Fe films on Pt result in an ordered alloy layer of 2 x 2 structure. However, detailed atomistic study has not been carried out. Here, we report scanning tunneling microscopy (STM) study on the growth of Fe on Pt(111) and the alloying processes by heating. All experiments were performed in ultrahigh vacuum of a base pressure below 2 x 10@super -8@ Pa. Pt surface was cleaned by cycles of Ar@super +@ ion bombardment at 1 keV and subsequent annealing in vacuum to 1300 K. Surface cleanliness was monitored by XPS and STM observation. Fe (99.999 %) was deposited onto the Pt(111) surface by an e-beam evaporator. STM observation was carried out at room temperature, and electrochemically etched tungsten tips were used. After 1.1 ML Fe deposition at room temperature, two-dimensional Fe islands up to three stories were formed and the Pt substrate was still visible, which is reasonable in terms of surface free energy. After annealing to 800 K, diffusion of Fe occurs and a network structure consisting of Fe and Pt atoms appears on the surface. After annealing to 1070 K, 2 x 2 structure was locally formed at the step edges, which corresponds to the reported alloy structure by Jerdev et al. It is also found that the surface includes defective structure as well as phase boundaries. The growth of Fe on Pt(111) as well as detailed alloying processes are discussed. @FootnoteText@ @footnote 1@ L-J. Wan et al., Chem. Comm. 2002 (2002) 58.@footnote 2@ D. I. Jerdev et al., Surf. Sci. 513 (2002) L391.