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MM: Fachverband Metall- und Materialphysik

MM 31: Topical session (Symposium MM): Fundamentals of Fracture

MM 31.3: Vortrag

Mittwoch, 14. März 2018, 11:00–11:15, TC 006

Influence of large strains on the properties of dislocation cores in silicon: is a dislocation can initiate a crack? — •Laurent Pizzagalli, Julien Godet, and Sandrine Brochard — Institut Pprime, CNRS UPR 3346, Université de Poitiers, Poitiers, France

It is now well established that a usually brittle material like silicon can be plastically deformed at room temperature, if one considers low dimensional systems such as thin films, nanowires, nanopillars, or nanocubes. In these latter, due to the lack of bulk sources, the onset of plasticity usually occurs through the nucleation of dislocation from surfaces, and at large strains typically greater than 5%. The influence of these large strains on the properties of dislocation cores is usually overlooked and is currently unknown. We have investigated the properties of silicon 60° dislocation in these conditions, by performing atomistic calculations using several interatomic potentials, a tight-binding approach, and density functional theory. We found that the stability of the dislocation core is highly dependent on the imposed strain. In particular, it is revealed that a dislocation core could initiate a crack opening in conditions of bi-axial tension. Alternatively, we found that the formation of a localized disordered zone is favored in the case of bi-axial compression. These points constitute a possible explanation of the observed brittle-ductile transition as a function of size in nano-objects. Besides, this work also suggests that empirical interatomic potentials are not appropriate to describe dislocations in such conditions.