The Brittle to Ductile Transition and the core structures of dislocations in silicon

It is now admitted that perfect shuffle dislocations control the plasticity of silicon in the high stress low temperature domain and dissociated glide dislocations in the high temperature low stress domain. The BDT appears then relevant to the transition between these two domains of “plasticity”.

Unlike dissociated glide dislocations, core computations of perfect dislocations show that various core configurations can exist for a given dislocation. Some of these cores are sessile and differently from metals, these sessile dislocations cannot be mobilized under stress promoting the nucleation of crack [2]. TEM experiments have shown that perfect dislocations nucleated in the brittle domain possess very efficient pinning points the density of which increases with temperature [2], [3]. Those pinning points appear to be intrinsic and relevant to some parts of sessile perfect dislocation cores. This induces a shut off of the perfect dislocations sources and a severe discontinuity in the apparent mobility of available dislocations close to the BDT, the consequences of which will be discussed.

[1] J Rabier, P Cordier, T Tondellier, J L Demenet, H Garem , Journal of Physics: Condensed Matter 12, 10059 (2000)

[2] J. Rabier, L. Pizzagalli, J. L. Demenet, Elsevier B. V., 16, 47 (2010)

[3] T. Okuno, H. Saka,, Journal of Materials Science, 48, 115 (2013)