Comparative Performance of Fluorite-Structured Materials for Nanosupercapacitor Applications

Abstract

Over the last fifteen years, ferroelectric and antiferroelectric ultra thin films based on fluorite-structured materials have drawn significant attention for a wide variety of applications requiring high integration density. Antiferroelectric $Zr{O}_2$, in particular, holds significant promise for nanosupercapacitors, owing to its potential for high energy storage density (ESD) and high efficiency ($\hat{I}\cdot$). This work assesses the potential of high-performance $H{f}_{1-x}Z{r}_x{O}_2$ thin films encapsulated by TiN electrodes that show linear dielectric (LD), ferroelectric (FE), and antiferroelectric (AFE) behavior. Oxides on silicon are grown by magnetron sputtering and plasma-enhanced atomic layer deposition. ESD and $\hat{I}\cdot$ are compared for FE, AFE, and LD samples at the same electrical field (3.5 MV/cm). As expected, ESD is higher for the FE sample ($95J/c{m}^3$), but $\hat{I}\cdot$ is ridiculously small ($\approx$ 55%), because of the opening of the FE hysteresis curve inducing high loss. Conversely, LD samples exhibit the highest efficiency (nearly 100%), at the expense of a lower ESD. AFE $Zr{O}_2$ thin film strikes a balance between FE and LD behavior, showing reduced losses compared to the FE sample but an ESD as high as $52J/c{m}^3$ at 3.5 MV/cm. This value can be further increased up to $84J/c{m}^3$ at a higher electrical field (4.0 MV/cm), with an $\hat{I}\cdot$ of 75%, among the highest values reported for fluorite-structured materials, offering promising perspectives for future optimization.