Energy induced nanoparticle substrate interactions

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Established top-down or bottom-up syntheses methods for nanoparticles often work close or even at thermodynamic equilibrium and are challenged by solubility limits or surface reconstructions. An alternative option is the subsequent modification of prepared nanoparticles by means of energy impact in a specific environment in order to develop new nanostructured materials with unusual or even exotic properties. Even more general, the functionality of nanoparticles is given by the occurring interaction processes with specific environments and/or supporting substrates upon a given energy impact! Thus, the evolution and reactions at interfaces, especially e.g. between nanoparticles and supporting substrates, are of great importance. Different chemical and physical processes take place at multiple scales: e.g. chemical reactions occur solely at atomic scales, thermal heat impact leads to the formation of interface alloys, and processes such as ion impact results in ballistic mixing of atoms. Even though several aspects have already been studied separately, a uniform and consistent picture of all involved processes has not been formulated and obtained until now. Identification of similarities and differences in nanoparticle substrate interactions induced by physical and/or chemical energy in specific environments would, on one hand, promote developing new materials with exceptional properties, and, on the other hand, specify their functionality.Exactly this challenge will be addressed in our joint proposal. We aim to identify the general impact of chemical and physical energy on the interaction between metallic nanoparticles and Si-based substrate materials in order to gain a deep understanding of the underlying processes. To achieve this goal, we will experimentally study chemical and physical effects on supported metal nanoparticle arrays taking place during energy impact by (a) heat, (b) ion irradiation, and (c) chemical reactions. Nanoparticle substrate interactions upon laser irradiation are vastly investigated, and the published results will be used to draw comprehensive conclusions together with our experimental results. The structural evolution will be monitored with various high-resolution techniques including electron microscopy, electron dispersive X-ray spectroscopy, electron back scattered diffraction, and atomic force microscopy. The three parallel approaches, with our chemical and physical background, will allow us the separation and the determination of the interplay of the underlying mechanism and effects. Surface and interface energies/forces at the nano-scale, different crystallographic orientations, phase diagrams, plastic flow, catalytic reactions and chemical bonding will and must be also considered besides alloying and ballistic mixing in order to obtain a full and valid understanding of nanoparticle-substrate interactions upon energy impact.