Order-Disorder Ferroelectric Transition of Strained SrTiO3

TL;DR

This study reveals that strained SrTiO3 undergoes an order-disorder ferroelectric transition characterized by nanometer-sized polar domains, contrasting with unstrained films, and provides insights into the nature of its ferroelectric behavior.

Contribution

The paper demonstrates that the ferroelectric transition in strained SrTiO3 is an order-disorder type, using advanced microscopy to observe nanoscale polar regions.

Findings

Strained SrTiO3 exhibits nanometer-sized polar domains at room temperature.

Unstrained SrTiO3 does not show these polar domains and remains paraelectric.

The ferroelectric transition in strained SrTiO3 is identified as an order-disorder transition.

Abstract

SrTiO3 is an incipient ferroelectric that is believed to exhibit a prototype displacive, soft mode ferroelectric transition when subjected to mechanical stress or alloying. We use high-angle annular dark-field imaging in scanning transmission electron microscopy to reveal local polar regions in the room-temperature, paraelectric phase of strained SrTiO3 films, which undergo a ferroelectric transition at low temperatures. These films contain nanometer-sized domains in which the Ti columns are displaced. In contrast, these nanodomains are absent in unstrained films, which do not become ferroelectric. The results show that the ferroelectric transition of strained SrTiO3 is an order-disorder transition. We discuss the impact of the results on the nature of the ferroelectric transition of SrTiO3.