Gold clusters: the role of the ion energy in their formation Elsa Thune (1)* , Ettore Carpene (1) , Katharina Sauthoff (2) , Michael Seibt (2) and Petra Reinke (1) (1) Zweites Physikalisches Institut, Universität Göttingen, Bunsenstrasse 7-9, D-37073 Göttingen, Germany (2) Viertes Physikalisches Institut, Universität Göttingen, Bunsenstrasse 13-15, D-37073 Göttingen, Germany * ethune@gwdg.de ABSTRACT The rapidly growing interest in the deposition of size-selected nanoclusters on surfaces is motivated both by technology and by basic physical questions. Due to their finite size, small particles have totally different material properties compared to their bulk crystalline counterparts. Clusters have been deposited by a monoenergetic, mass-selected ion beam with low energies (10-500 eV) on amorphous carbon substrates, which are used to minimize the influence of surface crystallography and ion-induced structural changes. Gold clusters were deposited as a model system to study the ion energy dependence, the temporal evolution, and the influence of the temperature on the cluster distribution. For impact energies below 100 eV, surface processes dominate the cluster nucleation and growth. If higher energies are used, an increasing number of ions is implanted below the surface and different processes control the cluster formation. When the energy increases above 350 eV, the cluster size drastically drops below 5 nm. The clusters are analysed with different methods such as Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM), and X-Ray Photoelectron Spectroscopy (XPS) to determine their size distribution, composition and structure. INTRODUCTION A cluster deposited on a surface constitutes a system with specific properties determined by the morphology, the material of the cluster, and the interaction between the cluster and the surface. It is of fundamental importance to study the evolution of the properties as a function of the cluster size, e.g., the morphology and the closely related electron density of states determining its physical and chemical properties [1, 2]. Deposited clusters have proven to have potential for a wide range of technological applications, such as catalysts [3], optoelectronics, nanocircuits, magnetic devices, metal-ceramic sensors, mechanically high strength granular materials, coatings, etc. [4]. Au clusters were deposited as a model system on silicon substrates coated with a thin amorphous carbon layer to study the dependence of the deposition parameters on their formation, in particular the energy influence. When the energy is lower than 1 eV, thermal deposition of species and low particle mobility are the most important phenomena. In the regime up to about 20 eV the ion energy exceeds the atom surface binding energy, surface defects are created and chemical reaction is initiated. For energies up to about 100 eV, shallow implantation is possible but sputtering is still negligible. Extended surface defects will be formed in crystalline surfaces. For higher energies up to 1000 eV sputtering and roughening of surface are predominant and the formation of buried layers and clusters occurs. Mat. Res. Soc. Symp. Proc. Vol. 777 © 2003 Materials Research Society T8.3.1