IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Friday Sessions
       Session SS3-FrM

Paper SS3-FrM4
Core Level Shifts and Stress at the Ni/W(110) Interface@footnote *@

Friday, November 2, 2001, 9:20 am, Room 122

Session: Clean and Adsorbed Surfaces
Presenter: R.T. Franckowiak, Utah State University
Authors: R.T. Franckowiak, Utah State University
N.D. Shinn, Sandia National Laboratories
B. Kim, Pohang Light Source, South Korea
K.J. Kim, Pohang Light Source, South Korea
T.-H. Kang, Pohang Light Source, South Korea
D.M. Riffe, Utah State University
Correspondent: Click to Email
Stress can play an important role in determining the structure and stability of heterogeneous interfaces. A recent STM and strain study@footnote 1@ of Ni overlayers on W(110) identified a pseudomorphic (1x1), and incommensurate (8x1) and (7x1) phases that exhibit compressive, tensile, and compressive stress, respectively. Interfacial electronic structure was suggested as the origin of the unexpected compressive stress in the (1x1) phase, rather than simple lattice mismatch in the adsorbed Ni film. This hypothesis was tested by measuring the W(4f) core-level binding energy shifts of interfacial W atoms during Ni overlayer growth. Photoemission spectra were obtained at the National Synchrotron Light Source, Brookhaven National Laboratory, using photon energies between 60 at 110 eV at a resolution of 150 meV. For the compressive pseudomorphic phase, interface W atoms exhibit a shift (compared to the bulk W) of -210 meV, whereas the 8x1 and 7x1 phases induce much smaller shifts of -90 and -120 meV, respectively. These shifts, which cannot be interpreted in terms of simple W-Ni coordination arguments, suggest that the interface tungsten electronic structure is very different in the pseudomorphic phase compared to the denser phases, and thus may be the source of the stress observed in the pseudomorphic phase. The similar W(4f) shifts in the 8x1 and 7x1 phases, which exhibit tensile and compressive stress, indicate that these stresses result from the Ni adlayer, as is expected from simple strain arguments based on the bulk Ni lattice constant. @FootnoteText@ @footnote 1@D. Sander, C. Schmidthals, A. Enders, and J. Kirschner, Phys. Rev. B 57, 1406 (1998). @footnote *@Supported by the DOE-BES Division of Materials Sciences. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000.