Nucleation,Growth, and TEM Analysis of Metal Particles and Clusters Deposited in UHV

It has been established for some time [1, 2] that small supported metal particles can be reproducibly prepared in a controlled way by ultrahigh vacuum (UHV) deposition onto planar supports. Such planar deposits have been employed in the past to study the physical [3–11] and chemical [12–20] properties of mesoscopic metal aggregates. In these studies, the emphasis has usually been placed on pointing out the differences in particle properties with respect to the bulk properties of the same material. Although it has often been found that the electronic properties reach bulk values at surprisingly small cluster sizes of about 30 to 50 atoms, it has also been observed that the chemical properties can change over a much wider particle size range [21] for structure-sensitive reactions [22]. Furthermore, it is generally realized that particle size alone is usually not the only important parameter but that the influence of the support in terms of electronic, structural, chemical, and morphological particle properties can be essential. which demonstrates the importance of experimental attempts to control the support properties as well as the particle properties.