Micro Fracture Mechanics in SEM

Fracture experiments using micrometer-sized specimens are an important tool to better understand the basis of the involved fracture mechanisms. To create such miniaturized fracture specimens, a variety of specimen production techniques are available at the ESI. Foremost, the focused ion beam (FIB) workstation is used for production of micrometer sized fracture specimens. Furthermore, assisting techniques such as ion polishing or lithography in cooperation with industrial partners are employed. For fracture experiments, the specimen type of choice are notched cantilevers and the possibilities are widespread, as these experiments enable to probe only a very limited volume. This can be useful for probing selected microstructural features, thin films, or irradiated materials.

Brittle and high strength materials as well as dielectric materials for semiconductor applications are tested involving linear elastic fracture mechanic. However, in-situ fracture experiments using single crystalline tungsten demonstrated that elastic plastic fracture mechanic has to be used for evaluation, as a comparatively large amount of plasticity is evident close to the crack tip – even at room temperature. With a wide range of experimental setups at hand, we are currently expanding our field of research to fracture mechanics applied to thin films and thin wires

Micro-cantilever featuring a FIB made notch. The micrograph was taken post-mortem after performing an in-situ experiment in the scanning electron microscope. Fractured W beam

S. Wurster, C. Motz, and R. Pippan: Characterization of the fracture toughness of micro-sized tungsten single crystal notched specimens. Phil. Mag. 92, 1803 (2012)