According to Physorg:
The scientists, Tadashi Ishida from the University of Tokyo and coauthors from other institutions in Japan and France, have published their study on the nanoscale plasticity of silicon in a recent issue of Nanotechnology.
Although some researchers have predicted that macroscopically brittle materials like silicon and other covalent materials (whose atoms are held together by strong covalent bonds) should show plasticity at the nanoscale, measuring the properties of nanosized materials is difficult for technical reasons. Some of the main difficulties include finding ways to securely clamp the material’s ends and monitoring the properties during testing.
To overcome these difficulties, the scientists used a novel method involving a microelectromechanical system and a transmission electron microscope, which they call MEMS-in-TEM. With this set-up, the researchers could simultaneously manipulate the silicon using the MEMS device while observing the results in real time with the microscope.
“The superplasticity was induced by the aggregate of stress-induced apparent circulation and intergranular baggy deformation, including apparent silicon nano grains.”
In stress-induced surface diffusion, the first of the two factors, the silicon atoms spread across the surface to increase the length of the nanobridge, which occurs due to mechanical tension and stress. The second factor, intergranular amorphous deformation, can be described as a “creep-like” flow of the intergranular material in the silicon, and the nanocrystals adjusting to this flow. The scientists’ observations suggest that, when the diameter of the nanobridge becomes comparable to the average size of the nanocrystals, the nanobridge reaches its critical yielding point and cannot elongate any further.
Article Source: Physorg.com