Influence of electric current on diffusionally accommodated sliding at hetero-interfaces

Abstract

Diffusionally accommodated sliding at metal/non-metal interfaces has been experimentally and analytically investigated under a combination of an interfacial shear stress and a superimposed electric current. It is demonstrated that interfaces slide faster if electron flow is in the direction of applied shear on the metal side of the interface, which causes the stress-driven diffusional flux flowing along the interface to be augmented by the interfacial flux due to electromigration (EM). Conversely, the sliding rate decreases if electrons flow opposite to the shear direction on the metal side, which causes the stress- and electromigration-induced fluxes to counteract each other. The contribution of electric current to sliding is significant only when a sufficient EM flux is associated with the interface, a situation which is common in modern electronic devices. An analytically derived constitutive model describing the kinetics of EM-influenced interfacial sliding is proposed. Consistent with experiments, the model predicts that the sliding kinetics have linear dependencies on stress and current density, and an Arrhenius dependence on temperature, with an activation energy equal to that for interfacial diffusion when the grain size is large and the temperature is relatively low. At small grain sizes, both interfacial and film diffusivities contribute to sliding, and the constitutive behavior becomes more complex.