  Plastic response due to dislocation activity under intense electric fields is
proposed as a source of breakdown. A model is formulated based on stochastic
multiplication and arrest under the stress generated by the field. A critical
transition in the dislocation population is suggested as the cause of
protrusion formation leading to subsequent arcing. The model is studied using
Monte Carlo simulations and theoretical analysis, yielding a simplified
dependence of the breakdown rates on the electric field. These agree with
experimental observations of field and temperature breakdown dependencies.
