Template-Controlled Growth of Model Catalysts

Before we discuss the template-controlled growth of model catalysts in more detail, we will have to consider a few aspects of STM imaging of these systems. This will be crucial for the characterization of the model catalyst surfaces. 

A more detailed picture of the temperature dependence of the growth is given in Figure 2.4, where the island density is plotted as a function of temperature. It can be seen that only in the temperature range from 207 to 288 K the growth is perfectly template controlled and the number of islands matches the number of available nucleation sites. This illustrates the importance of kinetic control for the creation of ordered model catalysts by a template-controlled process. Obviously, there has to be a subtle balance between the adatom mobility on the surface and the density of template sites (traps) to allow a template-controlled growth. We will show more examples of this phenomenon below. 

Oxide surfaces, and in particular oxide films, are versatile substrates for the preparation of model catalysts. Quite a few of these systems show nanoscale reconstructions, which can be employed as templates for the growth of ordered model catalysts of reduced complexity. In order to efficiently control the growth of nanostructured metal particle arrays, two conditions have to be met. First, the template must provide sites of high interaction energy that trap the deposited metals. Second, the kinetics of the growth process must be carefully controlled by choosing... 

The results for Pd and V lead to the conclusion that the high-symmetry sites of the alumina film on Ni3Al(l 1 1) can act as template for the growth of nanostructured model catalysts. They also prove that kinetic control of the growth is of utmost importance. 

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