  A large electric field is typically present in anodic or passive oxide films.
Stresses induced by such a large electric field are critical in understanding
the breakdown mechanism of thin oxide films and improving their corrosion
resistance. In this work, we consider electromechanical coupling through the
electrostrictive effect. A continuum model incorporating lattice misfit and
electric field-induced stresses is developed. We perform a linear stability
analysis of the full coupled model and show that, for typical oxides,
neglecting electrostriction underestimates the film's instability, especially
in systems with a large electric field. Moreover, a region where
electrostriction can potentially provide a stabilizing effect is identified,
allowing electrostriction to enhance corrosion resistance. We identified an
equilibrium electric field intrinsic to the system and the corresponding
equilibrium film thickness. The film's stability is very sensitive to the
electric field: a 40 percent deviation from the equilibrium electric field can
change the maximum growth rate by nearly an order of magnitude. Moreover, our
model reduces to classical morphological instability models in the limit of
misfit-only, electrostatic-only, and no-electrostriction cases. Finally, the
effect of various parameters on the film's stability is studied.
