AVS 50th International Symposium
    Surface Science Wednesday Sessions
       Session SS2-WeM

Paper SS2-WeM6
The Electronic and Geometrical Structures of Ultrathin Bimetallic Films of Pd and Cu on Ru(0001)

Wednesday, November 5, 2003, 10:00 am, Room 327

Session: Surface and Interface Structure: Metals
Presenter: J. Onsgaard, Aalborg University, Denmark
Authors: J. Onsgaard, Aalborg University, Denmark
L. Bech, Aalborg University, Denmark
Z. Li, University of Aarhus, Denmark
T.H. Andersen, University of Southern Denmark
S.V. Hoffmann, University of Aarhus, Denmark
Correspondent: Click to Email
Alloying conditions, low-dimensional effects and catalytical properties of ultrathin bimetallic films of Pd and Cu have been studied. Codeposition of the two metals on a relative inert substrate, Ru(0001), with overlayer thicknesses in the range 1 ML to 4 ML, were carried out. Deposition temperatures were either room temperature or 550 K and the thin films were characterized as a function of temperature. The information is based upon photoelectron spectroscopy based upon use of synchrotron radiation with high resolution core level studies of Pd 3d, Ru 3d, Cu 2p and valence band measurements. LEED was used to follow the order of the overlayers. Cu and Pd are distributed in one layer with temperature dependent mixing when the total coverage is one monolayer. The valence bands of the surface alloys are characterized by the Cu 3d band separated from the Pd 4d band at a temperature of 550 K. Heating causes hybridization of the Cu 3d and Pd 4d bands with formation of a new band between the individual metal bands. Surface alloying takes place at 660 K and above this temperature the structures of the overlayers are independent of the order of deposition. Cu 2p core-level binding energy shifts show two linear relationships with the composition of the film in 2-and 3 dimensions. An effect which is attributed to the different coordination numbers between Pd and Cu in 2- and 3 dimensions.