The miniaturization of electronic devices is the mayor economical driving force in nanotechnology, and consequently, traditional lithographic fabrication techniques are currently being pushed towards their size resolution limits. This is generating a need for research into alternative fabrication strategies, which can provide smaller structures. At present, these structures are predominantly of fundamental interest since size dependent phenomena such as Coulomb blockade effects' and conductance quantisation are beginning to play an important role and can be studied. Two very promising approaches to smaller structures and devices are nano-manipulation using scanning probe microscopes such as atomic force (AFM) and scanning tunneling microscopes (STM), and self-assembly. While the former can be applied quite readily to the fabrication and imaging of surface confined structures with atomic or molecular precision, the latter could, in principle, be exploited for the inexpensive mass fabrication of self-assembled nano-objects and devices. This would resemble the chemical synthesis of a large number of precisely defined molecules, only on a somewhat larger size scale. The possibility of such chemical nanofabrication is demonstrated by biological systems, which are, without exception, entirely constructed in this way. Artificial self-assembling systems are of course substantially different in that they are lacking organizational complexity and tend to develop towards the formation of thermodynamically stable structures. The controlled fabrication of even very simple nanostructures by self-assembly is at present still challenging, and the future development of a technology based on self-assembly would first require a thorough understanding of the physicochemical factors that govern self-organization processes. Some important factors include the size, shape and chemical nature of the building blocks, the chemical nature and topography of the substrate and the properties of the medium in which the processes are taking place. In the context of ongoing work on nanostructure self-organisation from gold nanoparticles we present here a brief overview of our recent results on the use of templates for the directed self-assembly of linear structures. Examples of two different systems are given to illustrate the importance of particle reactivity in one case, and that of substrate topography in the other.
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