Deformation behavior of thin copper films on deformable substrates

The role of strain hardening for the deformation of thin Cu films was inves tigated quantitatively by conducting specialized tensile testing allowing t he simultaneous characterization of the film stress and the dislocation den sity as a function of plastic strain. The stress-strain behavior was studie d as a function of microstructural parameters of the films, such as film th ickness (0.4-3.2 mum), grain size and texture. It was found that the stress -strain behavior can be divided into three regimes, i.e. elastic, plastic w ith strong strain hardening and plastic with weak hardening. The flow stres ses and the hardening rate increase with decreasing film thickness and/or g rain size, and are about two times higher in (111)-grains compared to the ( 100)-grains. These effects will be discussed in the light of existing model s for plastic deformation of thin films or fine grained metals. (C) 2001 Ac ta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.