Reduced coercive field in epitaxial thin film of ferroelectric wurtzite Al0.7Sc0.3N

Epitaxial ferroelectric wurtzite films exhibiting clear polarization-electric field hysteresis behavior are presented. The coercive field of this epitaxial Al0.7Sc0.3N film on the 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 Å smaller c-axis lattice parameter in the epitaxial film. The strain and decrease in the coercive field most likely originate from epitaxial strain rather than the mismatch in the thermal coefficient of expansion. These results provide insight for further coercive field reduction of wurtzite ferroelectrics using epitaxial mismatch strain.