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2017  Nov 1 - Dec 21

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2018  Apr 11 - Jun 4
2018  Proposal/BTR deadline: 2/1/18

Stress Distributions and Texture Formation in Thin Metal Films with Mixed Texture
Presented by:  Aaron M. Vodnick, Baker Group, Cornell

Thin metal films are often subjected to extreme stresses due to differential thermal expansion with the substrates to which they are attached. Such stresses can lead to failure in nano- and micro-fabricated devices, thus there is much interest in understanding the stress states in such films. Many mechanical characterization methods treat films as a continuum, analyzing the “macroscopic” behavior by assuming a biaxial stress state. However, metal films tend to be highly oriented, with microstructures consisting of only a few preferred crystallographic orientations which may deform very differently. X-ray diffraction is a convenient tool to probe the strains within each orientation separately, in real time, and at elevated temperatures. Both texture evolution and stress development were measured in thin Cu and Ag films during thermal cycling. Results show stress inhomogeneities dominate the thermomechanical behaviors, with texture interactions producing large three-dimensional stress sates.