AVS 45th International Symposium
    Surface Science Division Monday Sessions
       Session SS1-MoM

Paper SS1-MoM4
Photoelectron Spectroscopy Studies of Adhesion, Alloying and Segregation in the Platinum - Tungsten Bimetallic System

Monday, November 2, 1998, 9:20 am, Room 308

Session: Issues in Surface Electronic Structure
Presenter: J.J. Kolodziej, Rutgers University
Authors: J.J. Kolodziej, Rutgers University
T.E. Madey, Rutgers University
J.W. Keister, North Carolina State University
J.E. Rowe, North Carolina State University
Correspondent: Click to Email
High resolution soft X-ray photoelectron spectroscopy (SXPS) using synchrotron radiation, and Auger electron spectroscopy, are used to study Pt films on W (211). It is found that the films grow in layer-by-layer mode at 300 K. As a function of Pt film thickness four different Pt 4f@sub7/2@ photoemission peaks are observed, corresponding to a single monolayer of Pt/W, a Pt interface layer, Pt surface atoms and Pt bulk atoms. A single monolayer of Pt is stable up to the onset of desorption. In contrast, when multilayer Pt films are annealed above 600 K, substrate W atoms diffuse in the Pt overlayer to form an alloy. Evidence for a dilute alloy, in which the W 4f@sub7/2@ signal from the W impurity in a Pt host is found to have a binding energy 1 eV higher than bulk W, is observed up to 900K. The evolution of the bimetallic Pt - W sample as a function of Pt coverage and annealing temperature is diagnosed by analysis of intensities and angular dependencies of the W 4f@sub7/2@ and Pt 4f@sub7/2@ features. In all cases a single monolayer of Pt "skin" covers the alloy film. The data provide detailed information on energetics of adhesion, segregation and alloying in an early d - late d transition metal system.