Cyclic bulge testing is a versatile technique for measuring fatigue properties of freestanding thin films and has given important insights into failure mechanisms of ultrathin metal films. The fundamental deformation mechanisms induced by the cyclic loading are, however still not fully understood. Therefore, it is of great importance to combine cyclic bulge testing with high-resolution structural characterization techniques. In the present work, we present a new experimental setup that allows to combine intermittent transmission electron microscopy (TEM) imaging with bulge testing. A special interchangeable holder is designed that allows to image the same location after different cycles. This allows to directly image the contribution of dislocation or grain boundary processes on the deformation and damage of the thin film and enables observing the influence of microstructure and film thickness on the overall fatigue properties. A combination of bright-field scanning TEM (STEM) for dislocation imaging and 4D-STEM for orientation mapping is used to reveal deformation mechanisms induced by cyclic loading of 150 nm freestanding gold films.

This work was supported by the German Research Foundation (DFG) [grant ME-4368/8, Project 428963851] and the Austrian Science Fund (FWF) [Project I 4384-N, Y Y1236-N37].