Giant energy storage ultrafast microsupercapacitors via negative capacitance superlattices

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Abstract
Dielectric electrostatic capacitors, 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. Additionally, state-of-the-art electrochemical miniaturized energy storage systems – microsupercapacitors and microbatteries – currently face safety, packaging, materials, and microfabrication challenges preventing on-chip technological readiness, leaving an opportunity for electrostatic microcapacitors. Here we report record-high energy storage density (ESD) and power density (PD) across all electrostatic systems in HfO2-ZrO2 (HZO)-based thin film microcapacitors integrated directly on silicon, through a three-pronged approach. First, to increase intrinsic energy storage, atomic-layer-deposited antiferroelectric HZO films are engineered near a field-driven ferroelectric phase transition to exhibit amplified charge storage via the negative capacitance (NC) effect, which enhances volumetric-ESD beyond the best-known back-end-of-the-line (BEOL) compatible dielectrics (115 J-cm−3). Second, to increase overall stored energy, superlattice engineering of amorphous-templated HZO-Al2O3 heterostructures scales-up the high-storage antiferroelectric-NC behavior to the 100 nm regime, which overcomes the conventional thickness limitations of HZO-based (anti)ferroelectricity (10-nm regime). Third, to increase storage-per-footprint, the superlattices are conformally integrated into three-dimensional (3D) capacitors, which boosts areal-ESD (areal-PD) 9-times (170-times) the best known 3D electrostatic capacitors: 80 mJ-cm−2 (300 kW-cm−2). This simultaneous demonstration of ultrahigh ESD and PD overcomes the traditional capacity-speed trade-off across the electrostatic-electrochemical energy storage hierarchy. Furthermore, integration of ultrahigh-density and ultrafast charging thin films within a BEOL-compatible process enables monolithic integration of on-chip microsupercapacitors, which opens the door for substantial energy storage and power delivery for electronic microsystems.

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