Faculté des sciences

Experimental evidence for kinetically determined intermixed Volmer-Weber growth in thin-film deposition of Au on Ag(110)

Hayoz, J. ; Pillo, Th. ; Fasel, R. ; Schlapbach, Louis ; Aebi, Philipp

In: Physical Review B, 1999, vol. 59, no. 24, p. 15975-15989

Au films, from the submonolayer range up to 11 ML, have been deposited in situ at 300 K. The geometrical structures of these films have been investigated combining full-hemispherical x-ray photoelectron diffraction, low-energy electron diffraction (LEED), low-energy ion-scattering spectroscopy, and scanning tunneling microscopy leading to an intermixed Volmer-Weber growth model. The results... Plus

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    Summary
    Au films, from the submonolayer range up to 11 ML, have been deposited in situ at 300 K. The geometrical structures of these films have been investigated combining full-hemispherical x-ray photoelectron diffraction, low-energy electron diffraction (LEED), low-energy ion-scattering spectroscopy, and scanning tunneling microscopy leading to an intermixed Volmer-Weber growth model. The results demonstrate that below 0.5 ML most Au atoms are buried within the second substrate layer, forming inverted Ag/Au areas on the surface. The ejected Ag atoms and vacancies created during the Au-Ag exchange nucleate into elongated two-dimensional Ag islands and vacancy clusters, respectively, quickly breaking up the surface into smaller terraces. Above about 0.5-ML coverage, the Au-Ag exchange mechanism continues to be active. In addition, due to the reduced mobility of Au atoms deposited on inverted Ag/Au areas, one-dimensional Au stripes as well as elongated three-dimensional (1×3)-symmetric Au islands are observed already at submonolayer coverages on inverted Ag/Au areas. Only after the deposition of more than 8-ML Au is the Ag substrate completely covered, and missing-row reconstructed terraces extend over regions large enough to yield a well-defined 1×2 LEED pattern. The growth model is compared to both, published thermodynamic equilibrium predictions and molecular-dynamics simulations, revealing that the Au/Ag(110) growth system is kinetically determined.