  The influence of depolarizing field on the magnitude and stability of a
uniform polarization in ferroelectric capacitors and tunnel junctions is
studied using a nonlinear thermodynamic theory. It is predicted that, in
heterostructures involving strained epitaxial films and metal electrodes, the
homogeneous polarization state may remain stable against transformations into
the paraelectric phase and into polydomain states down to the nanoscale. This
result supports the possibility of depolarizing-field-related resistive
switching in ferroelectric tunnel junctions with dissimilar electrodes. The
resistance on/off ratio in such junctions is shown to be governed by the
difference between the reciprocal capacitances of screening space charges in
the electrodes.
