Atomic Layer-Deposited Interlayers for Robust Metal-Polymer Interfaces

The development of materials for flexible electronics and space applications critically depends on the mechanical integrity of metal thin films deposited on polymer substrates. However, film cracking and interfacial delamination at the metal-polymer interface limit the performance significantly. In this work, we demonstrate enhanced adhesion and electromechanical properties of magnetron-sputtered aluminum films on polyimide substrates through the introduction of an amorphous AlO_xH_y interlayer deposited via atomic layer deposition (ALD). Employing in situ X-ray diffraction and electrical resistance measurements during uniaxial and equi-biaxial tensile testing, we reveal that our integrated ALD-PVD approach yields an up-to-3-fold increase in both the crack onset and electronic failure strains and doubles the adhesion energy of the system. The AlO_xH_y interlayer alters interface-driven deformation mechanisms from absorbing to blocking dislocations at the interface. The strengthened metal-polymer interface, in turn, improves electromechanical stability at expanded strain ranges, resulting in shorter and more angled cracks in the metal film. This enhanced strain tolerance opens up alternative pathways for the development of flexible thin film devices that can conform to complex curved surfaces and withstand deformation while maintaining their functional properties.