Tuning Ag/Si(100) island size, shape, and density

Ag islands grown by depositing Ag onto Si(100) heated to 300-500 °C populate two distinct families. "Big islands" have basal dimensions in the few hundred nm to μm range, while "small islands" have basal diameters in the 10s of nm range. Big islands are clearly faceted, their bases are crystallographically aligned with the substrate and their bases form in a variety of shapes. Small islands are mound-like and not clearly faceted. The dependence of big island density on deposition temperature reveals that they form via nucleation and growth with a nucleation energy of 0.73 eV. The small island size and density are insensitive to growth temperature, indicating that they form via precipitation of Ag contained in a planar layer between the big islands that is thicker than the room-temperature Stranski-Krastanov layer. The big islands exhibit peculiar anti-coarsening behavior during anneals at their growth temperature: their areal density increases and their size decreases. Moreover, the proportion of each distinct basal shape evolves during the anneal and the big islands generally trend toward a more elongated shape. Since the small islands do not exist at the elevated growth and annealing temperatures, their size and density are relatively unaffected by annealing parameters. The results presented here provide guidance for tuning Ag/Si(100) island size, shape, and areal density that could have import for integration of plasmonics with Si devices.