Self-assembled hexagonal Au particle networks, 2–12 μm in cell size, on silicon have been achieved by a simple method. Honeycomb structure of Au nanoparticles on silicon was drop cast from the Au nanoparticle solution under appropriate concentration, evaporation rate, substrate temperature, and humidity. Hexagonal networks with discrete Au particles were generated in samples annealed in N2 ambient. Two-step annealing, i.e., annealing at 400 °C followed by annealing at 1000 °C for 1 h each was found to be effective to improve the regularity of the Au particle network. As the cell size can be adjusted by the tuning of the deposition conditions, the scheme promises to be an effective patterning method without complex lithography.

Long-range order, uniform in size, and regular in shape two-dimensional (2-D) arrays of core-shell structure Au nanoparticles have been synthesized. A reaction involving the displacement of the outer shells from tetraoctylammonium bromide (TOAB) to dodecanethiol (DT) molecules was used to form Au@TOAB-DT nanoparticles at room temperature (RT). The displacement reaction has used both superior size and shape control of Au@TOAB nanoparticles and uniform dispersion capability of Au@DT nanoparticles to achieve an extraordinarily large in extent (3 µm ϫ 3 µm), regular nanoparticle lattice structure. From ultraviolet (UV)-visible spectra, it was inferred that the interaction between the inner core and outer shell of Au@TOAB nanoparticles is weaker than that of Au@TOAB-DT and Au@DT samples. As a result, the ability of the TOAB outer shell to protect the Au@TOAB nanoparticles is weaker so that the system is more prone to agglomerate. On the other hand, the strong interactions between the inner core and outer shell for Au@TOAB-DT and Au@DT nanoparticles led to a predominantly 2-D structure.

Long-range order of uniform in size and regular in shape 2D arrays of Au@TOAB-DT nanoparticles (4.9 nm) were formed by a displacement reaction of the outer-shells from tetraoctylammonium bromide (TOAB) to dodecanethiol (DT) molecules at room temperature. The displacement reaction has utilized both superior size and shape control of Au@TOAB nanoparticles and uniform dispersion capability of Au@DT nanoparticles to achieve an extraordinarily large in extent (3 µm × 3 µm) regular nanoparticle lattice structure.Self-assembled NiSi quantum dot arrays have been grown on relaxed epitaxial Si 0.7 Ge 0.3 on (001)Si. The formation of the one-dimensional ordered structure is attributed to the nucleation of NiSi nanodots on the surface undulations induced by step bunching on the surface of SiGe film owing to the miscut of the wafers from normal to the (001)Si direction. The two-dimensional, pseudo-hexagonal structure was achieved under the influence of repulsive stress between nanodots.