Role of layer order on the equi-biaxial behavior of Al/Mo bilayers

Abstract

Thin film architectures with brittle and ductile material layers are often combined for functionality. Easy to fracture brittle films are often necessary due to their function as diffusion barriers, adhesion or protective layers. Especially in the field of flexible and wearable electronics brittle materials may cause short lifetimes. Direct current magnetron sputtered bilayers on a polyimide substrate containing brittle Mo and ductile Al layers (Al/Mo/PI and Mo/Al/PI) as well as Al films (Al/PI) were subjected to equi-biaxial loading with in-situ X-ray diffraction measurements. The setup enabled the extraction of the stress and full width at half-maximum as a function of the strain. The data yields deeper insights into underlying deformation and fracture mechanisms and the significance of the layer arrangement. It will be demonstrated that for stretchable applications the position of the Mo layer affects the fracture strain of the bilayers and the individual layers.