The effect of dislocation nature on the size effect in Indium Antimonide above and below the brittle-ductile transition
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.369
The effect of dislocation nature on the size effect in Indium Antimonide above and below the brittle-ductile transition J.M. Wheeler1,2, L. Thilly3, Y. Zou1, A. Morel2, R. Raghavan2,4 and J. Michler2 1ETH
Zürich Laboratory for Nanometallurgy Department of Materials Science Vladimir-Prelog-Weg 5, Zürich CH-8093, Switzerland Email: [email protected]
2Empa,
Swiss Federal Laboratories for Materials Science and Technology Laboratory for Mechanics of Materials and Nanostructures Feuerwerkerstrasse 39, Thun CH-3602, Switzerland
3Institut
Pprime, CNRS-University of Poitiers-ENSMA, SP2MI, Futuroscope 86962, France
4Department
of Materials Engineering Indian Institute of Science Bangalore – 560012, India
ABSTRACT The effect of length scale on mechanical strength is a significant consideration for semiconductor materials. In III-V semiconductors, such as InSb, a transition from partial to perfect dislocations occurs at the brittle-to-ductile transition temperature (~150 °C for InSb). High temperature micro-compression reveals InSb to show a small size effect below the transition, similar to ceramics, while in the ductile regime it shows a size effect consistent with fcc metals. The source truncation model is found to agree with the observed trends in strength with size once the change in Burgers vector and bulk strength are taken into account.
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INTRODUCTION: At the micro- and nano-scale, the characteristic size of the specimen frequently has a significant effect on the mechanical behaviour: as the size decreases, the strength is observed to increase 1, 2. In the case of compression of single crystalline micro- and nano-pillars and over moderate size ranges, ~1 order of magnitude, the behaviour can be empirically described using a power law relationship with the form: , (1), where σy is the yield strength, σ0 is the bulk strength, A and x are constants, and d is the characteristic size (e.g. diameter) also called “extrinsic” size in opposition to “intrinsic” size associated to internal microstructure size (e.g. grain size in polycrystalline samples). Notably, there is no consensus in the literature on the definition of the yield strength, σy, at small scales. Depending on the more or less discrete nature of plastic deformation (i.e. with or without strain bursts), many different criteria have been used. These have been based on arbitrary strain offset values, and compared directly with each other, although the values may then be associated to different regimes of plastic deformation (with or without hardening). It should be also mentioned that the crystallographic orientation of the different samples should be carefully taken into account since single or multiple slip orientations are expected to lead t
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