How to avoid FIB-milling artefacts in micro fracture? A new geometry for interface fracture

Focused ion beam (FIB) based small-scale fracture studies have been well established in recent years despite the ongoing discussion of possible artefacts caused by FIB milling. Stable crack growth geometries—where the FIB-prepared notch stably propagates through the sample—have the potential to ameliorate some of the FIB-based challenges. In this work, we propose a new sample geometry for testing interface toughness at the micron scale which results in intrinsically stable crack growth. This geometry is straightforward to fabricate using established FIB-based methods and testing setups. We prove the stability of crack growth by finite element modelling and by experimentally applying the approach on a hard coating–silicon interface. We observe that even with small imperfections, the FIB-milled notch propagates towards the interface and the natural crack stably grows along the interface.