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 Td{≥}700 K and {Θ}{}2/3 ML for Td{≤}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 Eᵣ to become embedded, with a gain in energy Eₑ. We find Eᵣ=1.90, Eₑ=0.60, and Eₐ=2.45, all ±{}0.05 eV, where Eₐ is the adatom adsorption energy. Possible structural and microstructural models and the interpretation of the energy Eᵣ are discussed.