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Annihilation of free volumes and internal stresses in nanocrystalline metallic layers

(Kopie 3)

Project Leader: Prof. H. Schmidt (Dr. rer. nat)

Funding period: 2010 - 2015
Funding body: DFG
Funding reference: -

Depending on their manufacture using suitable depositing methods (e.g. magnetron sputtering), nanocrystalline metals in the form of thin layers may be in a high-level state of non-equilibrium. Annealing at temperatures close to room temperature result in structural relaxation processes, which are associated with with a change in concentration of free volumes in the grains and grain boundaries over time. In particular, there is a correlation with the relaxation of residual stresses. Through these processes, electrical, mechanical and magnetic properties can change irreversibly.

The objective of this project is the experimental characterisation and modelling of these processes in thin metal layers (5 -150 nm). To this end an innovative method is to be used, which is based on the simultaneous in-situ measurement of lattice constants using X-ray diffractometry (XRD) and macroscopic length alteration with X-ray reflectometry (XRR) during isothermal annealing. Through the use of synchrotron radiation, a time resolution of less than a minute can be achieved. Using this method, various cubic nanocrystalline metals (Cu, Pd and Fe) with varying crystal structures and thicknesses, as well as an application-relevant nanocrystalline nitride compound (-TiNx) are to be systematically studied as a model system. From the results, an understanding is to be gained with regard to structural relaxation kinetics in relation to temperature, layer thickness and grain size.

 

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