  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 $ZrO_2$, in particular, holds significant promise for
nanosupercapacitors, owing to its potential for high energy storage density
(ESD) and high efficiency ($\eta$). This work assesses the potential of
high-performance $Hf_{1-x}Zr_{x}O_2$ 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 $\eta$ 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 ($95 J/cm^3$), but $\eta$ 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 $ZrO_2$ thin film strikes a balance between
FE and LD behavior, showing reduced losses compared to the FE sample but an ESD
as high as $52 J/cm^3$ at 3.5 MV/cm. This value can be further increased up to
$84 J/cm^3$ at a higher electrical field (4.0 MV/cm), with an $\eta$ of 75%,
among the highest values reported for fluorite-structured materials, offering
promising perspectives for future optimization.
