Regensburg 2016 – scientific programme

Parts | Days | Selection | Search | Updates | Downloads | Help

MM: Fachverband Metall- und Materialphysik

MM 40: Topical session: In-situ Microscopy with Electrons, X-Rays and Scanning Probes in Materials Science IV - Atomic structure and defects III

MM 40.3: Talk

Wednesday, March 9, 2016, 16:30–16:45, H38

Fracture toughness of freestanding gold thin films studied by bulge testing — •Eva Preiß, Benoit Merle, and Mathias Göken — Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Materials Science & Engineering, Institute I, Germany

A versatile bulge test setup was used to perform mechanical tests on rectangular gold membranes with columnar microstructure and thicknesses ranging from 100 nm to 350 nm. It can be used in a conventional way to calculate stress-strain curves and determine parameters such as residual stress and plane-strain modulus. Alternatively, the setup can be inserted into an atomic force microscope (AFM) which allows in-situ imaging of the topography of the deforming membrane.

In order to determine the fracture toughness of thin films, narrow crack-like slits of 10 um length were milled into the center of the membranes by focused ion beam (FIB). Subsequently, the membranes were loaded until rupture.

The fracture toughness of all tested gold films is much lower than the literature value for bulk gold. However, the fracture toughness remains constant within the investigated thickness regime. In-situ AFM scans of the crack tip region show stable crack growth before failure. Plastic deformation is localized to a narrow corridor in front of the crack tip and mainly takes place along grain boundaries.

The obtained fracture toughness values agree well with literature values for other metallic thin films. New insights from the in-situ AFM scans are discussed with regard to possible deformation mechanisms.