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We developed ultra-high energy storage density capacitors using a new class of lead-free bismuth pyrochlorebased dielectric film material systems with high breakdown strength and reliability. The 2 μm-thick pyrochlore ceramic film capacitors have demonstrated ultra-high energy densities around 90 J/cm3 with very low energy loss below 3%, which is achieved by the combination of high permittivity, pseudo-linear dielectric characteristics, and high breakdown electric field over 4.5 MV/cm. Particularly, these pyrochlore ceramic films can endure voltage strength up to ~900 V. These noteworthy pyrochlore ceramic films are fabricated by the lowcost chemical solution deposition process which allows dielectric films to be processed on standard platinized silicon wafers. This new class of capacitors can satisfy the emergent needs for significant reduction in size and weight of capacitors with high energy storage capability in power electronics, electric vehicles, and energy storage in sustainable energy systems. Our research provides a unique and economical platform for the processing of this useful pyrochlore material in large volume for eco-friendly energy applications. 

Abstract The device concept of ferroelectric-based negative capacitance (NC) transistors offers a promising route for achieving energy-efficient logic applications that can outperform the conventional semiconductor technology, while viable operation mechanisms remain a central topic of debate. In this work, we report steep slope switching in MoS₂transistors back-gated by single-layer polycrystalline PbZr_0.35Ti_0.65O₃. The devices exhibit current switching ratios up to 8 × 10⁶within an ultra-low gate voltage window of$$V_{{{\mathrm{g}}}} = \pm \! 0.5$$ $V_g=\pm 0.5$V and subthreshold swing (SS) as low as 9.7 mV decade⁻¹at room temperature, transcending the 60 mV decade⁻¹Boltzmann limit without involving additional dielectric layers. Theoretical modeling reveals the dominant role of the metastable polar states within domain walls in enabling the NC mode, which is corroborated by the relation between SS and domain wall density. Our findings shed light on a hysteresis-free mechanism for NC operation, providing a simple yet effective material strategy for developing low-power 2D nanoelectronics.