Movimento de paredes de domínio ferroelétricas com luz: descrição teórica e investigação do fenômeno em materiais policristalinos
Abstract
Ferroelectrics are material exhibiting a spontaneous polarization that may be switched by
an electric external field. This behavior is provided to well-known ferroelectric domain
walls motion. Recent research has proved the surprising ability to move ferroelectric
domain wall under illumination with wavelength of 532 nm incident on a surface of
single crystals of Barium Titanate (BaTiO3). In spite of experimental results concerning
about this light-matter interaction, it is remarkable a lack of physical insight, as well as
possibility to observe if occurrences of motion domain wall is due to single or poly crystal
character. By using a phenomenological approaches based on Devonshire-Landau’s theory
was possible make a development to describe a polarization-induced switching under light
like perturbation of bound and free charge accumulated within domain wall. Accordingly,
interactions between photons having lower energy that optical gap and screening charge
give rise to fluctuation in depolarization electric field that serve as a driving force to
polarization reorientation around the wall. This approach gives a satisfactory explanation
to experimental facts observed in single crystals of BaTiO3, in addition, it allows to
conjecture a correlation between the phenomenon occurrence with existence of charged
domain wall as single crystal as polycrystal. It was prove that BaTiO3 coarse grain ceramics
(grain size approx 50µm) contend 90-domains are possible a manifestation of polarization
switching induced by light also, in this form, it was demonstrate the size grain dependence
with evidence of this light-matter interaction, highlighted again the role-play of charged
ferroelectric domain wall. In this way, here has made an extend to polycrystal materials
that could lead to developed the next generation of photo-stimulated ferroelectric devices.