Giant energy storage and power density negative capacitance superlattices

Abstract

Dielectric electrostatic capacitors¹, due to their ultrafast charge-discharge capability, are attractive for high power energy storage applications. Along with ultrafast operation, on-chip integration can enable miniaturized energy storage devices for emerging autonomous microelectronics and microsystems^2-5. Additionally, state-of-the-art miniaturized electrochemical energy storage systems – microsupercapacitors and microbatteries – currently face safety, packaging, materials, and microfabrication challenges preventing on-chip technological readiness^2,3,6, leaving an opportunity for electrostatic microcapacitors. Here we report record-high electrostatic energy storage density (ESD) and power density (PD) in HfO₂- ZrO₂-based thin film microcapacitors integrated on silicon, through a three-pronged approach. First, to increase intrinsic energy storage, atomic-layer-deposited antiferroelectric HfO₂-ZrO₂ films are engineered near a field-driven ferroelectric phase transition to exhibit amplified charge storage via the negative capacitance effect^7-12, which enhances volumetric-ESD beyond the best-known back-end-of-the-line (BEOL) compatible dielectrics (115 J-cm^-3)¹³. Second, to increase total energy storage, antiferroelectric superlattice engineering¹⁴ scales the energy storage performance beyond the conventional thickness limitations of HfO₂-ZrO₂-based (anti)ferroelectricity¹⁵ (100-nm regime). Third, to increase storage-per-footprint, the superlattices are conformally integrated into three-dimensional capacitors, which boosts areal-ESD (areal-PD) 9-times (170-times) the best-known electrostatic capacitors: 80 mJ-cm^-2 (300 kW-cm^-2). This simultaneous demonstration of ultrahigh energy- and power-density overcomes the traditional capacity-speed trade-off across the electrostatic-electrochemical energy storage hierarchy^1,16. Furthermore, integration of ultrahigh-density and ultrafast-charging thin films within a BEOL-compatible process enables monolithic integration of on-chip microcapacitors⁵, which can unlock substantial energy storage and power delivery performance for electronic microsystems^17-19.