title: Room-temperature negative capacitance in a ferroelectric-dielectric superlattice heterostructure.
abstract: We demonstrate room-temperature negative capacitance in a ferroelectric-dielectric superlattice heterostructure. In epitaxially grown superlattice of ferroelectric BSTO (Ba0.8Sr0.2TiO3) and dielectric LAO (LaAlO3), 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 (SrTiO3 (001), DyScO3 (110), and GdScO3 (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.
authors.affiliation: Department of Electrical Engineering and Computer Sciences, University of California , Berkeley, California 94720, United States.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Gao
authors.forename: Asif
authors.initials: A
authors.lastname: Khan
authors.forename: Xavi
authors.initials: X
authors.lastname: Marti
authors.forename: Chris
authors.initials: C
authors.lastname: Nelson
authors.forename: Claudy
authors.initials: C
authors.lastname: Serrao
authors.forename: Jayakanth
authors.initials: J
authors.lastname: Ravichandran
authors.forename: Ramamoorthy
authors.initials: R
authors.lastname: Ramesh
authors.forename: Sayeef
authors.initials: S
authors.lastname: Salahuddin
keywords: Room-temperature negative capacitance; epitaxial strain; ferroelectric; superlattice