Self-Assembly and Thermal Stability of Binary Superlattices of Gold and Silicon Nanocrystals

Simple hexagonal (sh) AB(2) binary superlattices (BSLs) of organic ligand-capped silicon (A; 5.40(+/- 9.8%) nm diameter) and gold (B; 1.88(+/- 10.1%) nm diameter) nanocrystals were assembled by evaporation of colloidal dispersions and characterized using transmission electron microscopy (TEM) and grazing incidence small-angle X-ray scattering (GISAXS). When deposited on tilted substrates by slow evaporation, the sh-AB(2) superlattice contracted slightly toward the substrate with centered orthorhombic structure. Heating the BSL to 200 degrees C in air led to gold coalescence and segregation to the surface of the assembly without disrupting the Si nanocrystal sublattice, thus creating a sh superlattice of Si nanocrystals.