3 research outputs found
Manipulating Ferroelectric Domains in Nanostructures Under Electron Beams
Freestanding BaTiO3 nanodots exhibit domain structures characterized by
distinct quadrants of ferroelastic 90{\deg} domains in transmission electron
microscopy (TEM) observations. These differ significantly from flux-closure
domain patterns in the same systems imaged by piezoresponse force microscopy.
Based upon a series of phase field simulations of BaTiO3 nanodots, we suggest
that the TEM patterns result from a radial electric field arising from electron
beam charging of the nanodot. For sufficiently large charging, this converts
flux-closure domain patterns to quadrant patterns with radial net
polarizations. Not only does this explain the puzzling patterns that have been
observed in TEM studies of ferroelectric nanodots, but also suggests how to
manipulate ferroelectric domain patterns via electron beams.Comment: 5 pages, 6 figure
Influence of charged walls and defects on DC resistivity and dielectric relaxations in Cu-Cl boracite
Charged domain walls form spontaneously in Cu-Cl boracite on cooling through
the phase transition. These walls exhibit changed conductivity compared to the
bulk and motion consistent with the existence of negative capacitance. Here, we
present the dielectric permittivity and DC resistivity of bulk Cu-Cl boracite
as a function of temperature (-140 {\deg}C to 150 {\deg}C) and frequency (1 mHz
to 10 MHz). The thermal behaviour of the two observed dielectric relaxations
and the DC resistivity is discussed. We propose that the relaxations can be
explained by the existence of point defects, most likely local complexes
created by a change of valence of Cu and accompanying oxygen vacancies. In
addition, the sudden change in resistivity seen at the phase transition
suggests that conductive domain walls contribute significantly to the
conductivity in the ferroelectric phase.Comment: 9 pages, 4 figure