August 25, 2011 — A new nanoscale parameter discovered by Aalto University shows that silicon nanoparticles can be compressed to half their size without breaking. This deviation from bulk material properties (wherein silicon is brittle) could lead to new nanoscale device designs from on-chip lasers to drug delivery vehicles.
Researchers squeezed silicon spheres and tracked the resultant atomic rearrangements. Material response varied depending on the degree of deconfinement that contrasts the "size effect." Smaller material volumes displayed unexpected deformation mechanisms under mechanically induced shape changes.
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Bulk silicon displays plasticity characterized by phase transformations. However, less-constrained silicon nanoparticles deviate from this mechanical response, compressing to half their size without breaking. Researchers call this the "nanoscale confinement" parameter. They expect the phenomenon to resolve issues discovered in other studies, where silicon behaves differently at different sizes.
The study provides a basis for understanding the onset of incipient plasticity in nanovolumes. This is a repeatable process that could generate crystal structures to enhance Si’s functional properties and biocompatibility.
Professor Roman Nowak, Nordic Hysitron Laboratory, Aalto University led the research, in cooperation with the Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, while the calculations were consulted with Professor Risto Nieminen of CSC-IT / Aalto University.
The discovery is recently published in Nature Nanotechnology: D. Chrobak, N. Tymiak, A. Beaber, O Ugurlu, W.W. Gerberich and R. Nowak, Deconfinement leads to changes in the nanoscale plasticity of silicon, Nature Nanotechnology 6 (2011) 480-484. Access it here: http://www.nature.com/nnano/journal/v6/n8/abs/nnano.2011.118.html
The research was supported by the Academy of Finland, CSC-IT Center for Science (Finland), the Foundation of Helsinki University of Technology, Ceramic Society of Japan and National Science Foundation (USA).
Learn more at http://www.aalto.fi/en/ (English language version)