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A dynamic measurement system has been developed to investigate damping in thin metal films. This system includes a vacuum chamber, in which a free-standing bi-layer cantilever sample is vibrated using an electrostatic force, and a laser interferometer to measure the displacement and velocity of the sample. With this equipment, internal friction as low as 10−5 in micrometer thick metal films in the temperature range 300–800 K can be measured. Using this system, the internal friction of Cu thin films was measured and an activation energy of 1.47 ± 0.05 eV was obtained from the internal friction peaks. Based on the dependence of the internal friction on the temperature, the frequency and the thickness of the film, we suggest that this activation energy points to a dragging mechanism of jogs accompanied by vacancy diffusion along the dislocation core. The proposed mechanism is modeled and compared with experimental results.
Journal: Acta Materialia - Volume 54, Issue 3, February 2006, Pages 679–687