At the nanoscopic scale, the plastic deformation of crystalline materials proceeds by nucleation and motion of defects through the periodic stacking of atoms. The mobility of these defects - mainly dislocations and interfaces - is accordingly the factor which determines the mechanical properties as a function of stress and temperature. This shows the importance of understanding the structure of defects, and their mechanisms of motion.
The mobility of dislocations and interfaces are studied by transmission electron microscopy and/or in situ straining experiments in the electron microscope. Their individual and collective behaviours are then modelled at various scales, in order to determine the exact origin of the mechanical properties.
The materials studied are metals and alloys with various structures, semiconductors. Model materials are privileged to study elementary mechanisms.
Special attention is given to the plastic deformation of nanostructured materials and thin layers, where the mean-free path of defects is very small. This results in fairly high mechanical properties. Lastly, dislocations which strongly disturb the normal behaviour of semiconducting devices must be eliminated, which requires a good knowledge of their physical properties.
Research topics :
- Elementary mechanisms of plasticity
- Small Scale Plasticity
- Defaults and Integrated circuits materials
