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Silicon micropillars obtained by FIB from Floating Zone silicon single crystal have been deformed in situ in a SEM between room temperature and 400 °C. Pillars with <123> axis were studied in order to promote single slip deformation. Mechanical data as a function of pillar diameter and surface deformation microstructures observed by SEM are reported. Yield stresses as a function of temperature are compared with those resulting from high‐pressure tests (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Dedicated to Professor Dr. Wolfgang Schro È ter on the occasion of his 65th anniversary Low temperature deformation experiments of silicon under confining pressure are analyzed with reference to a possible transition at high applied stress t t between dissociated glide configuration and perfect shuffle as extrapolated from the calculations of Duesbery and Joos (Phil. Mag. Lett. 74, 253 (1996)) as well as the low temperature deformation experiments on compound semiconductors (CSC). It is shown that experiments performed at a higher value of the expected transition stress have not put forward the evidence of such a transition. The influence of a preexisting population of glide dislocations on such a transition in the deformation mechanisms is also discussed.

The flow stress of the wide band-gap semiconductor, 4H-SiC, has been measured by uniaxial compression tests over the temperature range 500–1400 °C at different strain rates. At low strain rates, 4H-SiC shows a transition in the yield stress at a temperature Tc. In addition, the brittle-to-ductile transition (BDT) temperature TBDT of the same material has been determined on precracked samples at different values of strain rate ε̇ by 4-point bend tests. Intriguingly, the transition temperature Tc in yielding is very close to the brittle-to-ductile transition temperature TBDT in the fracture behavior. In previous transmission electron microscopy (TEM) investigations, significant microstructural differences were found between low-temperature (T&lt;Tc) and high-temperature (T&gt;Tc) deformed crystals. There, the results showed that in the samples deformed below the transition temperature Tc, deformation proceeds by the generation and motion of single leading partial dislocations on different (0001) planes. Moreover, all the partials appeared to have the same core, silicon. On the other hand, at temperatures above Tc, the samples deformed by the generation and motion of perfect dislocations dissociated in the form of leading/trailing partial pairs separated by a ribbon of stacking fault. Based on the present mechanical tests and previous TEM results—together with experimental evidence from other semiconductors—a model is presented in which Tc and TBDT are identified and correspond to the temperature at which crystal shear takes place by different dislocation types. Below Tc, single leading partials are responsible for crystal shear, whereas above Tc, perfect dislocations (i.e., leading/trailing pairs) accomplish the slip. Since generation of a leading partial from crack tip sources basically shuts the sources off, the crystal remains brittle below this transition temperature. At Tc=TBDT, trailing partials are nucleated from the same sources to clean up the stacking fault and allow multiplicative generation of dislocation avalanches resulting in transition to the ductile mode.