Biaxial Zero Creep Measurements of Interface Energies in Ni/Ag Multilayers

Abstract

Biaxial zero creep experiments were performed on Ni/Ag multilayer films on sapphire substrates. The equilibrium curvature was measured using a scanning laser and position sensitive photodetector. The experiments were designed to measure the free energy of Ni/Ag interfaces and to investigate their effect on the structural stability of multilayered materials. For the Ni/Ag multilayers studied, significant plastic straining occurs at temperatures above 400°C, enabling the growth stresses and thermal stresses in the multilayers to decay to zero. After a long time at elevated temperatures, the equilibrium curvature is reached for the film/substrate couple. This curvature is determined by the number and the energy of the Ni/Ag interfaces. Using this equilibrium technique, a free energy of 0.44 ± 0.03 N/m was measured for Ni/Ag interfaces at an equilibrium temperature of 550°C.