  We report on the electric field response of 180 degree nanodomain walls in
BaTiO$_3$ using in situ electrical biasing in transmission electron microscopy
(TEM). The sample is biased on a micro-device designed for reliable testing
whose key attributes are confirmed by finite element calculations. The presence
of weakly charged zig-zag 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 behaviour. All effects are
measured locally and directly from the imaged domain structure.

Applied Physics;Materials Science