Room-Temperature Negative Capacitance in a Ferroelectric–Dielectric
Superlattice Heterostructure
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Abstract
We demonstrate room-temperature negative
capacitance in a ferroelectric–dielectric
superlattice heterostructure. In epitaxially grown superlattice of
ferroelectric BSTO (Ba<sub>0.8</sub>Sr<sub>0.2</sub>TiO<sub>3</sub>) and dielectric LAO (LaAlO<sub>3</sub>), capacitance was found to
be larger compared to the constituent LAO (dielectric) capacitance.
This enhancement of capacitance in a series combination of two capacitors
indicates that the ferroelectric was stabilized in a state of negative
capacitance. Negative capacitance was observed for superlattices grown
on three different substrates (SrTiO<sub>3</sub> (001), DyScO<sub>3</sub> (110), and GdScO<sub>3</sub> (110)) covering a large range
of substrate strain. This demonstrates the robustness of the effect
as well as potential for controlling the negative capacitance effect
using epitaxial strain. Room-temperature demonstration of negative
capacitance is an important step toward lowering the subthreshold
swing in a transistor below the intrinsic thermodynamic limit of 60
mV/decade and thereby improving energy efficiency
