Electric-field-induced monoclinic phase in (Ba,Sr)TiO$_3$ thin film

TL;DR

This study demonstrates electric-field-induced symmetry lowering to a monoclinic phase in (Ba,Sr)TiO$_3$ thin films, confirmed through polarized Raman spectroscopy showing domain and phonon mode changes.

Contribution

It provides experimental evidence of electric-field-induced monoclinic phase transition in (Ba,Sr)TiO$_3$ thin films using Raman spectroscopy.

Findings

Presence of c-domains confirmed at zero field

Splitting and hardening of E(TO) soft mode under electric field

Monoclinic symmetry observed via Raman spectra

Abstract

We have studied electric-field-induced symmetry lowering in the tetragonal (001)-oriented heteroepitaxial (Ba$_{0.8}$Sr$_{0.2}$)TiO$_3$ thin film deposited on (001)MgO substrate. Polarized micro-Raman spectra were recorded from the film area in between two planar electrodes deposited on the film surface. Presence of \textit{c}-domains with polarization normal to the substrate was confirmed from polarized Raman study under zero field, while splitting and hardening of the \textit{E}(TO) soft mode and polarization changes in the Raman spectra suggest monoclinic symmetry under external electric field.