Reduced Coercive Field in Epitaxial Thin Film of Ferroelectric Wurtzite Al0.7Sc0.3N

TL;DR

This paper reports the first epitaxial ferroelectric wurtzite film demonstrating reduced coercive field due to epitaxial strain, offering insights for designing ferroelectrics with lower coercive fields.

Contribution

It introduces the first epitaxial ferroelectric wurtzite film with clear hysteresis and shows how epitaxial strain reduces coercive field compared to conventional films.

Findings

Epitaxial Al0.7Sc0.3N film exhibits a coercive field 8% smaller than conventional films.

The reduction is linked to a smaller c-axis lattice parameter due to epitaxial strain.

Epitaxial strain, not thermal mismatch, causes the coercive field decrease.

Abstract

The first epitaxial ferroelectric wurtzite film with clear polarization-electric field hysteresis behavior is presented. The coercive field of this epitaxial Al0.7Sc0.3N film on W/c-sapphire substrate is 0.4 +- 0.3 MV cm-1 (8 %) smaller than that of a conventional fiber textured film on a Pt/TiOx/SiO2/Si substrate, attributed to the 0.01 +- 0.007 {\AA} smaller c-axis lattice parameter in the epitaxial film. The strain and decrease of the coercive field most likely originate from epitaxial strain rather than the mismatch in thermal coefficient of expansion. These results provide an insight for further coercive field reduction of novel wurtzite ferroelectrics using epitaxial mismatch strain.