Microstructure control of thin films is of particular importance for improving the reliability of microdevices in terms of electromigra-tion, fatigue damage and hillocking. High-energy ion bombardment has turned out to be an appropriate modification instrument as it leads to selective grain growth, resulting in single-crystal-like structures. The current work addresses the effect of 7 MeV Au~+ and 1.5 MeV N~+ irradiation at high fluences (up to 45 X 10~(16) ions cm~(-2) on the microstructure and the mechanical properties of 500 nm Au thin films of small initial grain size (70-90 nm). The following microstructure changes were observed: selective grain growth, texture changes, sputtering, interfacial degradation, formation of geometrically necessary dislocations, and defect clusters. Hardening behavior was found to be a consequence of grain growth (Hall-Petch effect) and the formation of ion-induced defects.
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