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

Paper SS2-WeM4
Structural Evolution of an Atomically Rough Surface: Faceting and Alloying of Re(12-31)

Wednesday, November 5, 2003, 9:20 am, Room 327

Session: Surface and Interface Structure: Metals
Presenter: A.S.Y. Chan, Rutgers University
Authors: A.S.Y. Chan, Rutgers University
H. Wang, Rutgers University
W. Chen, Rutgers University
J.E. Rowe, United States Army Research Office
T.E. Madey, Rutgers University
Correspondent: Click to Email
The thermal stability of ultrathin metal and oxide films on an atomically rough Re(12-31) surface has been studied using Low Energy Electron Diffraction (LEED) and High Resolution Soft X-ray Photoelectron Spectroscopy (HRSXPS) using synchrotron radiation. Re(12-31) is a morphologically unstable surface with 6 surface layers of atoms exposed. This highly corrugated surface exhibits a surface shift in the Re4f core levels of 0.17 eV towards higher binding energy, relative to the bulk peak. Adsorption of oxygen at room temperature leads to a disordered chemisorbed oxygen overlayer with a rich distribution of chemical binding states, while the surface retains a planar morphology. However, when the O-precovered surface is annealed to temperatures above 700 K, drastic restructuring of the surface occurs to form nanosized facets with a ridged "hill-and-valley" morphology. The facet planes are identified as (01-10) and (11-21) based on kinematic simulations of LEED patterns, and are consistent with Field Emission Microscopy results of our collaborators. By controlling the coverage of oxygen, different oxygen coordination sites on the Re facet planes can be selectively populated and identified by distinct chemical shifts (up to 0.73 eV) to higher binding energies in the Re4f core levels. In contrast, the Re substrate does not facet when precovered with a Pt or Pd overlayer and annealed. Ultrathin Pt films form a dilute alloy with the Re substrate at temperatures as low as 300 K; this surface alloy becomes increasingly Re-rich as the film is annealed.