Mitigating the film–substrate decohesion in nanoporous metals

Substrate-supported films of dealloyed nanoporous metals spontaneously develop a low-connectivity layer at the film–substrate interface, impairing interfacial adhesion strength. Comparable interfacial degradation has been reported for sintered interconnects in microelectronics. The phenomenon arises from a divergence in the diffusive, curvature-driven flux of the material, normal to the interface. This reduces the local solute fraction and eventually leads to disconnection by a Plateau–Rayleigh-type instability. Comparing dealloying and subsequent coarsening in experiments and kinetic Monte Carlo simulation, this work investigates mitigation strategies and, in particular, the effect of distinct porosity–depth profiles on the interfacial connectivity. Two design principles are suggested: First, the profile should be smooth, avoiding jumps and kinks. Second, steep porosity gradients should be placed in low-porosity regions. Exponential profiles are found preferable for avoiding degradation. In the fields of nanoporous thin films as functional materials and of interconnects in microelectronics joining, the findings provide the basis for materials design toward enhanced adhesion and lifetime.