Abstract

Dielectric layers composed of metal oxides are routinely subjected to external electric fields during the course
of normal operation of electronic devices. Many phenomenological theories suggest that electric fields strongly
affect the properties and mobilities of defects in oxide films and can even facilitate the creation of new defects.
Although defects in metal oxides have been studied extensively both experimentally and theoretically, the effect
of applied electric fields on their structure and migration barriers is not well understood and still remains subject to
speculations. Here, we investigate how static, homogeneous electric fields affect migration barriers of canonical
defects—oxygen vacancies and interstitial ions—in a prototypical oxide, MgO. Using the modern theory of
polarization within density functional theory (DFT), we apply electric fields to defect migration pathways in
three different charge states. The effect of the field is characterized by the change of the dipole moment of the
system along the migration pathway. The largest changes in the calculated barriers are observed for charged
defects, while those for the neutral defects are barely significant. We show that by multiplying the dipole moment
difference between the initial and the transition states, which we define as the effective dipole moment, by the
field strength, one can obtain an estimate of the barrier change in excellent agreement with the DFT calculated
values. These results will help to assess the applicability of phenomenological models and elucidate linear and
nonlinear effects of field application in degradation of microelectronic devices, electrocatalysis, batteries, and
other applications.