The Template Route to Nanostructured Model Catalysts

The fabrication of such a system can be accomplished only by nanofabrication, and different routes can be imagined in this context. We will focus in the following section on the template-controlled growth of metal clusters on thin oxide films, which has proven to give excellent results in terms of low complexity. This approach has been successfully employed for metal-on-metal systems (for a comprehensive review see [6]) and has recently been extended to metal growth on oxide films. 

The key factor in this approach is the provision of suitable growth templates. Before we turn to this point, we will discuss in which way surfaces may be thought of as templates. 

To fully exploit the nanoscopic properties of materials, for example, in catalysis, this structure size is much too large since it corresponds to a regime where the bulk properties of materials still dominate. An alternative approach can be the patterning of a surface by direct manipulation of atoms or molecules with the scanning tunneling microscopy (STM) [8], which has been successfully employed in the past 

The nanopatterning of a surface is, however, only the first step toward a surface template. We will further need a specific property of the surface, which is encoded into the pattern. Only this will assure that the template will control the subsequent nucleation or growth processes. In many cases, this specific property will be 

That not only an increased interaction energy at the traps can be responsible for a template-controlled growth but also an anisotropy of the surface diffusion 

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In this section the use of oxide surfaces as templates will be discussed. These surfaces are particularly interesting because of their potential use in industrial applications in which insulating or inert substrates are required. In this context one has to refer to nanocatalysts or electronic devices, which nowadays rely on an active patterning of the surface. Oxidic templates can be used for the fabrication of well-ordered model systems in these fields, fii fact the search for more powerful catalysts is often hampered by the fact that the complexity of the real world catalyst does not allow an in-depth investigation. Ordered nanostructured model catalysts prepared in a template-controlled process can provide a pathway to systems of lower complexity, which opens a route to the investigation of basic steps in heterogeneous catalysis. 

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