Local hard and soft pinning of 180° domain walls in BaTiO3 probed by in situ transmission electron microscopy

We report on the electric-field response of 180\ifmmode^\circ\else\textdegree\fi{} nanodomain walls in $\mathrm{BaTi}{\mathrm{O}}_{3}$ using in situ electrical biasing in transmission electron microscopy. The sample is biased on a microdevice designed for reliable testing whose key attributes are confirmed by finite element calculations. The presence of weakly charged zigzag domain walls at room temperature is attributed to the geometric confinement of the device. The motion of the domain walls under the applied electric field allows to extract local P-E loops where distinct domain-wall pinning in deep and random energy potential profiles, characteristic for ``hard'' and ``soft'' ferroelectrics, respectively, are observed. ``Hard'' domain-wall pinning results in asymmetrical loops typical for ``hard'' ferroelectrics while the ``soft'' domain-wall pinning follows Rayleigh-like behavior. All effects are measured locally and directly from the imaged domain structure.