Modeling the Effect of Varying Electrical Voltage on the Plastic Deformation of a Single Asperity in Hot-Switched RF MEMS Contacts

摘要

The pull-apart of a single asperity gold-gold contact with and without current flow was investigated using large-scale molecular dynamics simulations coupled to a continuum treatment of Joule heating and heat transfer. The initial interface geometry, which was derived from a finite element fractal model of a contact blunted by plasticity, contained an asperity with a contact area of 40nm~2 that was brought into contact with a flat substrate of area 1850nm~2. As the contact is pulled apart, the simulations show dislocation emission from steps in the substrate surrounding the asperity contact, as well as a nanowire being drawn between the surfaces with a radius much smaller than that of the initial asperity contact. The results indicate that both the wire-pulling and dislocation emission characteristics are highly dependent on the level of voltage applied, with a marked difference between constant voltage and constant current conditions.