In-situ TEM investigation of toughening in Silicon at small scales. (September 2021)

• Record Type: Journal Article
• Authors: Issa, Inas; Gammer, Christoph; Kolitsch, Stefan; Hohenwarter, Anton; Imrich, Peter J.; Pippan, Reinhard; Kiener, Daniel
• Is Part Of: Materials today. Volume 48(2021)
• Page Start: 29
• Page End: 37
• Publication Date: 2021-09
• Subjects: Size scale effect -- Fracture toughness -- Brittle Ductile Transition (BDT) -- Single crystal (SC) Silicon (Si) -- In-situ TEM -- Nanoscale fracture experiments -- Toughening; Materials science -- Periodicals; Metallurgy -- Periodicals; Metal-work -- Periodicals; Biomedical and Dental Materials -- Periodicals; Manufactured Materials -- Periodicals; Metals -- Periodicals; 620.11
• DOI: 10.1016/j.mattod.2021.03.009
• Languages: English
• ISSNs: 1369-7021

Abstract

Graphical abstract: Abstract: We report a length-scale-controlled Brittle-Ductile Transition giving rise to significant toughening of a commonly brittle material. Using quantitative in-situ Transmission Electron Microscopy (TEM) fracture experiments at room temperature on single crystal Silicon, we find that large samples fracture concordant with the brittle bulk behavior at a stress intensity K I C ~ 1 M P a . m 1 / 2 . Below characteristic dimensions of about 250 nm, however, the fracture toughness strikingly increases inversely with size to at least triple. As evidenced from advanced in-situ TEM nanoscale strain mapping the stresses at the crack tip approach the theoretical strength. At the same time, below this critical transition length nucleation and propagation of dislocations was observed, shielding the crack tip and enabling the unprecedented rise in fracture toughness. These first time in-situ TEM observations in nanoscale Silicon at room temperature open new strategies to simultaneously strengthen and toughen indispensable yet brittle functional materials solely by geometrical miniaturization.