Effects of Nanometer-Thick Passivation Layers on the Mechanical Response of Thin Gold Films

The mechanical behavior of freestanding gold membranes 0.5 μm thick with and without passivation layers was studied with a membrane deflection experiment. Membrane width was varied from 2.5 to 20 μm to investigate size effects. The presence of the passivation layer had the effect of reducing the membrane strength. Yield stress, as well as fracture strain and stress, were all found to be significantly lower for the passivated specimens. The residual stress state was found to be significantly larger with passivation, to the degree of generating prestressed cracks at micromachined notches. Membrane width had the greatest effect on the residual stress state with smaller widths having larger residual stress.