Temperature-dependent coverage of the √3 × √3R30° structure of Ag/Si(111)

The coverage Θ of the √3 × √3 R30° Ag/Si(111) interface has been measured by micro-Auger electron spectroscopy. With a dose of 5 monolayer (ML), we find Θ≊1 ML for deposition temperature ${\mathit{T}}_{\mathit{d}}$≥700 K and Θ≊2/3 ML for ${\mathit{T}}_{\mathit{d}}$≤620 K. Much smaller changes (≊0.05 ML) were observed during annealing. These effects are explained by a simple kinetic model in which ∼2 Ag atoms are readily incorporated into the structure, but a third atom must overcome an activation energy ${\mathit{E}}_{\mathit{r}}$ to become embedded, with a gain in energy ${\mathit{E}}_{\mathit{e}}$. We find ${\mathit{E}}_{\mathit{r}}$=1.90, ${\mathit{E}}_{\mathit{e}}$=0.60, and ${\mathit{E}}_{\mathit{a}}$=2.45, all ±0.05 eV, where ${\mathit{E}}_{\mathit{a}}$ is the adatom adsorption energy. Possible structural and microstructural models and the interpretation of the energy ${\mathit{E}}_{\mathit{r}}$ are discussed.