In-situ x-ray diffraction and the evolution of polarization during the growth of ferroelectric superlattices

TL;DR

This study uses in-situ synchrotron x-ray diffraction to monitor ferroelectric domain evolution, surface termination, and lattice parameters during the growth of BaTiO₃/SrTiO₃ superlattices, revealing how electrostatic boundary conditions influence ferroelectric properties.

Contribution

It introduces a rapid in-situ x-ray diffraction technique to observe ferroelectric domain evolution during superlattice growth, highlighting the role of boundary conditions.

Findings

Ferroelectric domains evolve during growth under certain boundary conditions.

Surface termination and lattice parameters are monitored in real-time.

Electrostatic boundary conditions significantly influence ferroelectric behavior.

Abstract

In epitaxially strained ferroelectric thin films and superlattices, the ferroelectric transition temperature can lie above the growth temperature. Ferroelectric polarization and domains should then evolve during the growth of a sample, and electrostatic boundary conditions may play an important role. In this work, ferroelectric domains, surface termination, average lattice parameter and bilayer thickness are simultaneously monitored using in-situ synchrotron x-ray diffraction during the growth of BaTiO$_3$/SrTiO$_3$ superlattices on SrTiO$_3$ substrates by off-axis RF magnetron sputtering. The technique used allows for scan times substantially faster than the growth of a single layer of material. Effects of electric boundary conditions are investigated by growing the same superlattice alternatively on SrTiO$_3$ substrates and 20nm SrRuO$_3$ thin films on SrTiO$_3$ substrates. These experiments provide important insights into the formation and evolution of ferroelectric domains when the sample is ferroelectric during the growth process.