Annihilation of free volumes and residual strain in nanocrystalline metal layers

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Topic of the present project is the basic understanding and mutual correlation of the following physical processes in materials: (1) relaxation of residual strain, (2) temporal change of vacancy concentration, (3) structural re-orientation of grains, and finally (4) self-diffusion processes. The time-resolved (minutes) determination of vacancy concentration, residual strain, and structural re-orientation is done with the newly developed method of Synchrotron based differential dilatometry. There, the lattice parameters and the film thickness are measured (quasi-)simultaneously in-situ during isothermal annealing by X-ray diffractometry and X-ray reflectometry. Investigation of self-diffusion (in grains and grain boundaries) in a stable nano-structure is accomplished with focusing neutron reflectometry on isotope multilayers. In order to obtain a reliable comparison of results, all experiments are carried out on the same type of samples. The planned fundamental research will help to understand microstructural and stress controlled processes in nano-crystalline metals and will also help to optimize the properties of these materials.