AVS 47th International Symposium
    Surface Science Monday Sessions
       Session SS2+NS+TF-MoM

Paper SS2+NS+TF-MoM7
Preferential Nucleation of Metal Nanoclusters on S(4x4)/W(111)

Monday, October 2, 2000, 10:20 am, Room 209

Session: Nucleation and Growth
Presenter: Q. Wu, Rutgers, The State University of New Jersey
Authors: Q. Wu, Rutgers, The State University of New Jersey
W. Chen, Rutgers, The State University of New Jersey
T.E. Madey, Rutgers, The State University of New Jersey
Correspondent: Click to Email
Interactions of several metals (Cu, Pt and Pd) with the highly ordered S(4x4)/W(111) surface have been studied by means of Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and scanning tunneling microscopy (STM). The substrate is a sulfur-induced nanoscale reconstruction of W(111) with (4x4) periodicity, characterized by broad, planar terraces (~ 30 nm in width). We find that fractional monolayers of vapor-deposited Cu grow as 3D clusters on the S(4x4) surface over a wide coverage range. At low Cu coverages (@<=@ 0.1 ML), Cu nanoclusters are observed to nucleate preferentially at characteristic 3-fold hollow sites on the S(4x4) surface; there is a clear energetic preference for one type of site over others. The formed Cu nanoclusters are uniform in size (~ 0.7 nm) up to 0.25 ML, indicating self-limiting growth. As coverage increases, additional sites are populated and Cu clusters grow in size. On the other hand, Pt and Pd exhibit a different behavior, disordering the (4x4) reconstruction and adsorbing beneath the outer S-layer. STM data are supported by LEED and AES measurements. The data are interpreted in terms of relative surface free energy, relative reactivity, and the metal-W, metal-S, and S-W binding energies, as supported by our previous TPD data.