Issue 47

P. Gallo et alii, Frattura ed Integrità Strutturale, 47 (2019) 408-415; DOI: 10.3221/IGF-ESIS.47.31 408 Focussed on “Crack Paths” Experimental characterization at nanoscale of single crystal silicon fracture toughness Pasquale Gallo, Takashi Sumigawa, Takayuki Kitamura Kyoto University, Kyoto-daigaku-Katsura, Nishikyo-Ku, Kyoto-Shi 615-8540, Japan pasquale.gallo@aalto.fi , http://orcid.org/0000-0001-5742-8647 sumigawa@cyber.kues.kyoto-u.ac.jp kitamura@kues.kyoto-u.ac.jp A BSTRACT . The work reviews some preliminary recent micromechanical tests aimed at the evaluation of the fracture toughness of silicon. Pre-cracked nano specimens and alternatively notched nano specimens combined with the theory of critical distances (TCD) are compared. The results show that the fracture toughness of silicon is approximately 1 MPa·m 0.5 , regardless of the procedure involved (i.e., pre-cracked samples or TCD). This value agrees with macro counterpart, i.e., 0.75-1.08 MPa·m 0.5 , and therefore the K IC is independent of the size and crystal orientation. However, by employing the TCD, the accurate control of the final crack tip which is currently very challenging, is overcome by using notched specimens. Additionally, the results give information about the crack propagation at the nanoscale. It seems that although the specimen axis deviates from the (011), the crack propagates along the cleavage plane (011) and the process develops very fast by breaking covalent bond at the crack tip. A brief discussion on beyond the breakdown of continuum theory and challenges toward nanometer scale fracture mechanics concludes the paper. K EYWORDS . Fracture nanomechanics; Silicon; Nanoscale; Fracture toughness; Citation: Gallo, P., Sumigawa, T., Kitamura, T., Experimental characterization at nanoscale of single crystal silicon fracture toughness, Frattura ed Integrità Strutturale, xx (2019) 408-415. Received: 26.10.2018 Accepted: 07.11.2018 Published: 01.01.2019 Copyright: © 2019 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION onventional fracture mechanics [1] has been primarily investigated starting from the II World War and developed in the well-known linear elastic fracture mechanics (LEFM). However, in the last decade, new challenges have arisen. Indeed, the miniaturization of electronic devices driven by the increasing demand for high-density integrations have brought problems of material behavior at very small scales into the domain of the conventional fracture mechanics [2]. Moreover, recent literature suggests that in many applications at the macroscale, reliable engineering for entire component lifetime depends on accurate prediction of fracture from the smallest size until final failure [3]. While numerical simulations have spread rapidly [4], the small sizes of micro and nanocomponents still impose several challenges for the experimental study of their mechanical properties. The mechanical characterization at the micro and nanoscale (or even at atomic scale [5]) provides essential parameters for the design of components such as Micro/Nano- C