Nonlinear flexural response of a suspended Au nanobeam structure undergoing an electromigration-lead breakdown

The nonlinear resonance response of electromechanical structures, such as Duffing resonators, can discern both geometrical and internal anomalies, such as the “softening” response attributed to deviations from an ideal parallel plane for the former and the “hardening” response attributed to internal strains for the latter. Herein, we study the evolution of the nonlinear resonance response of a suspended Au nanobeam structure undergoing a mechanical breakdown due to an electromigration-lead process. Nanogaps are formed by utilizing a feedback-controlled electromigration technique while simultaneously electrostatically driving the free-standing beam. The morphological evolution of the metallic nanobeam structures is further ascertained between feedback iterations by a scanning electron microscopy. We detect a rich nonlinear response when changing from softening to hardening, and vice versa, before the ultimate mechanical breakdown.