How does picosecond structural deformation of (Ba,Sr)TiO$_{3}$ relate to the pyroelectric effect?

TL;DR

This study investigates the ultrafast structural deformation in (Ba,Sr)TiO$_{3}$ thin films and its relation to the pyroelectric effect, using time-resolved measurements to better understand the complex interactions involved.

Contribution

It introduces a time-resolved approach to study picosecond structural deformation in ferroelectric thin films, providing increased sensitivity over traditional polarization hysteresis measurements.

Findings

Fast thermal expansion observed after femtosecond laser excitation.

Heat diffusion simulations suggest charge dynamics influence thermal behavior.

Further studies needed to quantify individual contributions to pyroelectricity.

Abstract

The pyroelectric effect in ferroelectric thin films is typically composed of different contributions, which are difficult to disentangle. In addition, clamping to the substrate interface plays an important role. We studied epitaxial (Ba,Sr)TiO$_3$ thin films grown on NdScO$_3$ to see if time-resolved measurements can shed more light on the complex interaction. In particular, we compare standard measurements of the pyroelectric coefficient by temperature-dependent hysteresis loops to transient deformation measurements on picosecond timescales in the same material. The advantage of the time-resolved approach lies in its increased sensitivity in thin films compared to that of polarization hysteresis measurements. Whereas a fast thermal expansion of the ferroelectric thin film was observed after femtosecond laser excitation of the intermediate SrRuO$_3$ layer, heat diffusion simulations reveal frustration of the thermal expansion, which might be explained with the charge dynamics at the Schottky barrier formed at the SrRuO$_3$/(Ba,Sr)TiO$_3$. More studies are required to quantitatively assess the individual contributions to the pyroelectric coefficient of the materials used in our layer architecture.