High-Tc BaTiO3 ferroelectric films with frozen negative pressure states

TL;DR

This study demonstrates that plasma processing can induce a negative pressure state in BaTiO3 ferroelectric films, significantly increasing their Curie temperature and ferroelectric properties, enabling high-temperature device applications.

Contribution

The paper introduces a plasma-based method to enlarge the unit cell volume and ferroelectric distortion in BaTiO3 films, achieving a record high Curie temperature.

Findings

Approximately 5% unit cell volume expansion.

Ferroelectric tetragonal distortion increased by about 4 times.

Curie temperature elevated by roughly 580 K compared to bulk crystals.

Abstract

We report that an energetic plasma process is extremely effective in enlarging the unit cell volume and ferroelectric distortion of the ferroelectric oxides, resulting in a significant increase in its Tc. We demonstrate experimentally that c-axis oriented BaTiO3 films can be deposited directly on quartz glass and Si substrates using such a process and that the material shows an approximately 5% expansion of its unit cell volume and approximately 4 times the ferroelectric tetragonal distortion of the bulk crystals. Such a frozen negative pressure results in a Tc value that is approximately 580 K higher than that of bulk single crystals, providing a wide range of operating temperatures for the devices. The present results suggest an approach to producing ferroelectric oxides with unique properties that might be extended to ferromagnetic or superconductor oxides and demonstrate a route to a lead-free ferroelectric oxide for capacitive, ferroelectric memory, and electro-optical devices.