Regensburg 2010 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 26: Poster Session

MM 26.26: Poster

Dienstag, 23. März 2010, 14:45–16:30, Poster C

Thickness Effects in Very High Cycle Fatigue Behavior of Cu Films — •Clemens Trinks, Felix Hebenstreit, and Cynthia A. Volkert — Institut für Materialphysik, Georg-August-Universität Göttingen

It has recently been established that decreasing the thickness of metal films leads to an increase in fatigue life and a change in fatigue damage morphology. This has been correlated with the high strength of thin films and attributed to their limited dislocation activity. The current research extends fatigue studies below 100 nm film thickness and to ultra high cycle numbers. Such studies are of great relevance for predicting the reliability of metal components used in micro- and nano-technology, where they often experience repeated, low-level mechanical or thermal-mechanical loading. A resonant cantilever method has been developed using an AFM to test and monitor the fatigue behavior of Cu films with thicknesses between 20 nm and 2 µm. Strain amplitudes up to 0.1 % and cycle numbers up to 10¹⁰ have been achieved. First results from a 200 nm thick film show evidence of narrow extrusions parallel and next to twin boundaries, as well as cracking and grooving at grain boundaries. This damage is similar to what is observed in low cycle fatigued films of similar thickness, giving first indications that the mechanisms of damage formation are determined predominately by the film thickness and not by the strain amplitude.