R.H. FOLK II, M. KHANTHA, D.P. POPE, V. VITEK, "Temperature-Dependent Onset of Yielding in Dislocation-Free Silicon: Evidence of a Brittle-to-Ductile Transistion", pp.161-167.
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Titre : R.H. FOLK II, M. KHANTHA, D.P. POPE, V. VITEK, Temperature-Dependent Onset of Yielding in Dislocation-Free Silicon: Evidence of a Brittle-to-Ductile Transistion, pp.161-167.

Auteur : R. H. Folk II
Auteur : M. Khantha
Auteur : D.P. Pope
Auteur : V. Vitek - Dept. of Materials Science and Eng., University of Pennsylvania, Phila. Pa., 19072

Stockage : Stéphane FORSTER et Thierry LEQUEU
Pages : 161 - 167

An investigation of the brittle-to-ductile transition (BDT) in silicon has been conducted on essentially dislocation-free
silicon test specimens made by photolithography. No pre-cracks or additional dislocation sources were introduced into the
samples. Three-point bending tests of the samples reveals a well defined transition from brittle fracture of the specimens
to complete yielding near 732°C at a crosshead displacement rate of 0.1 mm/min. Limited plasticity is observed below 732°C
but is insufficient to prevent crack propagation suggesting that yielding is not dislocation mobility limited. Instead the
transition may be controlled by the nucleation of a sufficient density of dislocations. Further support comes from the
results of experiments conducted at temperatures below 732°C in which samples were rapidly pre-loaded within the linearly
elastic regime, then immediately retested. This rapid pre-loading results in a lower transition temperature. This would not
be expected if dislocation mobility controlled the BDT. Instead, it is believed that the transition only occurs when a
sufficient density of dislocations has nucleated within the sample. In these experiments, the pre-loading event may increase
the dislocation nucleation rate. The source of the dislocations in these defect free samples is still under investigation.

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