Studies of Ag/Fe Interfacial Free Energies by Biaxial Zero Creep Experiments

Biaxial zero creep experiments based on the Josell model were performed on Ag/Fe multilayer thin films to determine their interfacial free energies. Various multilayer samples on stiff wafers prepared by RF magnetron sputtering were subjected to annealing of long duration at 550°C, while a substrate curvature technique was employed for real-time film stress monitoring. Sufficient plastic flow in films makes possible a zero creep equilibrium state to present during this isothermal process, and as a result the interfacial free energies in multilayer interfaces are equilibrated with the elastic strain energies arising from the substrate bending. There is no collapse in the annealed multilayer structures. They are still stably layer-built and exhibit a column grain distribution. XRD results show that Ag and Fe layers have (111) and (110) preferred orientations, respectively. In accordance with a revised Josell model, the equilibrium stresses were measured and the Ag (111)/ Fe (110) interface free energy at 550°C was found to be 0.97 ± 0.13 J/m 2.