The coupling of polarization and oxygen vacancy migration in ferroelectric Hf0.5Zr0.5O2 thin films enables electrically controlled thermal memories above room temperature

TL;DR

This study demonstrates that ferroelectric Hf0.5Zr0.5O2 thin films can be used to create electrically controlled thermal memories with hysteretic thermal conductivity, driven by polarization and oxygen vacancy migration coupling.

Contribution

It reveals a novel mechanism linking ferroelectric polarization and oxygen vacancy migration to enable non-volatile thermal memory states.

Findings

Thermal conductivity exhibits hysteresis with electric field.

Two stable thermal states (ON/OFF) with a ratio of 1.6.

Memory states are stable over time.

Abstract

Here we investigate epitaxial Hf0.5Zr0.5O2 ferroelectric thin films as potential candidates to be used as non-volatile electric-field-modulated thermal memories. The electric-field dependence of the thermal conductivity of metal/Hf0.5Zr0.5O2/YSZ devices is found to be hysteretic, resembling the polarization vs electric field hysteresis loops, being maximum (minimum) at large applied positive (negative) voltages from the top metallic electrode. This dynamic thermal response is compatible with the coupling between the ferroelectric polarization and the oxygen ion migration, in which the oxygen vacancies are the main phonon scattering sources and the polarization acts as an electrically active ion migration barrier that creates the hysteresis. This new mechanism enables two non-volatile thermal states: high (ON) and low (OFF) thermal conductivity, with an ON/OFF ratio of 1.6. Both the ON and OFF states exhibit high stability over time, though the switching speed is limited by ion mobility in the YSZ electrode.