Nano-sized metal particles assemblies

For electronics and nano-optical application particles are preferably composed out of a conducting metal such as gold, silver, copper, platinum, or at least a semi conductor such as silicon, cadmium sulfide, cadmium selenide or zinc oxide. To achieve efficient collective behavior noble metal colloids of either a high homogeneity in size and shape are required or a deep understanding of excitation modes (particle plasmons and extended plasmons, Figure 2) within particle assemblies is necessary. 

Metal colloids are assemblies of atoms with unique physical and chemical properties. These colloidal particles are nano-crystals or nano-amorphous lumps composed out of 2 to 10 atoms. which are bound together by crystal energy. Within the state of matter described by cluster-type behavior we define a nano-particle, nano-cluster, nano island, precipitate or- whatever name is used for these assemblies as a colloidal particle not specifying the size, shape or property of this assembly (Figure 1). 

A fundamental change in behavior is observed when reducing the size of the colloidal particle as a transition from macroscopic metals to semi -conductor-type colloids and further on to atom assemblies and isolated atoms. This transition to the isolating state is observed for most metals in between 2 and 100 atoms. A unique behavior is often observed if a magic number of atoms forms a defect-free nano-crystal. Gold in a perfect nano-crystal is even more stable against oxidation than a macroscopic gold metal sheet. 

NSL—often called colloidal lithography (CL)— is an effective technique using self-assemblies of polystyrene (PS) micro- or nano-particles on solid surfaces as 2-or 3-dimensional masks for metal deposition (Zhang et al. 2010). The size and shapes of the close-packed nanospheres and the holes between them, in addition to the metal deposition conditions, such as evaporation angle or specific deposition technique (e.g., sputtering, thermal deposition), influence the achieved metallic patterns. A different kinds of metallic nanostructures can he obtained (Fig. 3.10) ... 

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