Superior and ultrafast energy storage performance of relaxorantiferroelectric HfO2-based supercapacitors

Compared to electrochemical energy storage, dielectric thin film-based capacitors possess the advantages of higher voltage stability and higher break-down voltage as well as lower leakage current etc. Since HfO2 films are compatible to microelectronic process and its ferroelectricity is strategically important in memory device, the realization of their excellent energy storage comparable will broaden their applications in microelectronic devices. In this study, we utilized Al3+ dopant, known for its smaller ionic radius compared to Hf4+, to induce lattice disorder in the Hf0.5Zr0.5O2 films, facilitating transformation of the Hf0.5Zr0.5O2 film from ferroelectric to antiferroelectric, and ultimately to a superparaelectric-like relaxation antiferroelectric behaviors. We have experimentally demonstrated that, by introduction of an appropriate Al doping level of x= 4.13%, the Hf0.5Zr0.5O2 thin films with a relaxation antiferroelectric characteristic can achieve a corresponding recoverable energy density of more than 100 J cm−3, an efficiency of more than 80%, and an effective enhancement of the dielectric strength to more than 6 MV cm−1. Compared to HfO2-based amorphous/crystalline films reported previously, this is a record-high energy density in atomic layer deposited HfO2/ZrO2 ternary doped oxides, and beyond that, we also demonstrate their superfast charging/discharging as a capacitor. Targeting at high-speed supercapacitor applications in integrated circuit, HfO2-based dielectric may win the competition with perovskite oxides in terms of dielectric breakdown strength and charging/discharging speed etc. Our fundamental understanding of the physics behind also enriches the knowledge of materials science and dielectric physics.