X-ray microbeam diffraction study of strain in polycrystalline aluminum thin films

Thermally induced strains in polycrystalline Al films on glass and single crystal Si substrates have been examined on a grain-by-grain basis by x-ray microbeam diffraction. The crystallographic orientation and the deviatoric strain tensor, epsilon*ij, were determined for each measurement location by white beam Laue diffraction. From grain orientation mapping and strain tensor measurements, information was obtained about the distributions of strains for similarly oriented grains and about strain variations within single grains. Grain size, texture, and misorientation correlations with residual strains were also examined. Strains during thermal cycling and strain relaxation at room temperature were compared to model calculations. The mechanisms involved in these calculations during thermal cycling and during room temperature relaxation were studied. The grain boundary diffusivity for Coble creep used in the model calculations was also studied and recalculations were made that provide a better fit of the model calculations to the experimental data. The type of information gathered in this study may be useful in developing and testing theories for intergrain effects in strain evolution in polycrystals.; It was concluded from this study that many factors affect the mechanical behavior of thin films during thermal cycling and during room temperature relaxation, including grain size, texture, and grain orientation. The nature of the film-substrate interface may also affect the behavior of the films. The model calculations and parameters used in this study were not successful in predicting quantitatively thin film mechanical behavior. Microdiffraction measurements reveal that the strains on the inter- and intra-granular level are very different than the average strain in a film.