Tailoring of Ferroelectric Coercive Field and Polarization with Ferroelectric and Antiferroelectric HfxZr1-xO2 Bilayer Structure

In this letter, the advantages of an antiferroelectric (AFE) and ferroelectric (FE) bilayer stack made of Hf
_x
Zr
_1-x
O
₂
(HZO) with different compositions were reported. Compared to the monolayer ferroelectric control sample, Mo/FE/Mo, the Mo/FE/AFE/Mo, and Mo/AFE/FE/Mo stacks exhibited a significant decrease in the coercive field (E
_c
). A higher dielectric constant of AFE increased the voltage distribution across the FE layer in the bilayer HZO structure, leading to a decrease in E
_c
. Furthermore, the capacitor with Mo/AFE/FE/Mo exhibited 28% higher polarization, P
_r
(2P
_r
= 45.9 μC/cm
²
), than the control sample, while this significant increase of Pr was not observed in the capacitor with Mo/FE/AFE/Mo. Electrical measurements of the capacitors with FE and AFE having various thicknesses showed that the dielectric constants and phase composition depend on the deposition sequence. A higher orthogonal phase ratio was achieved in the Mo/AFE/FE/Mo stack compared to the Mo/FE/AFE/Mo stack, resulting in higher polarization. Furthermore, bilayer capacitors with Mo/AFE/FE/Mo showed more robust long time reliability, such as endurance and retention.