Irradiation of nanostructures - sputtering and embedding phenomena

Energetic ions interaction with matter is an interesting and fundamental aspect of materials modification. There are hardly any experimental studies to know the initial stages (first few pico seconds to nano seconds) of ion impact on a material. It is an established fact that ion bombardment on materials surfaces and interfaces plays a vital role in science and technology. For last five decades, most of the work is limited to ion-bulk solid interactions. Our recent results of ion impacts on nanostructures posed questions on basic understanding on ion - solid interactions at nano-scale. In this talk, energetic ions (ranging from few tens of keV to 100 MeV) interaction with nanostructured thin films is explored in the context of ion-beam-induced nanoscale mixing and embedding. Sputtering from isolated nanoislands found to be more compared to continuous and uniform films. Also, for gold nano-islands, MeV self-ion induces ion mixing at nanoscale regime and formation of nano-gold-silicide has been observed. Ion beam mixing found to be absent for thick and continuous films while it is prominent in isolated nanoislands. Surface nanoalloy formation was observed for Au-Ge system. Direct observation of collision cascade effects would be presented with some recent STEM data. RBS, HRTEM/STEM, AFM and X-ray methods are used for this study. (author)