Negative capacitance in a ferroelectric capacitor

Asif Islam Khan; Korok Chatterjee; Brian Wang; Steven Drapcho; Long You; Claudy Serrao; Saidur Rahman Bakaul; Ramamoorthy Ramesh; Sayeef Salahuddin

doi:10.1038/nmat4148

Negative capacitance in a ferroelectric capacitor

Nat Mater. 2015 Feb;14(2):182-6. doi: 10.1038/nmat4148. Epub 2014 Dec 15.

Authors

Asif Islam Khan¹, Korok Chatterjee¹, Brian Wang¹, Steven Drapcho², Long You¹, Claudy Serrao¹, Saidur Rahman Bakaul¹, Ramamoorthy Ramesh³, Sayeef Salahuddin⁴

Affiliations

¹ Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, USA.
² Department of Physics, University of California, Berkeley, California 94270, USA.
³ 1] Department of Physics, University of California, Berkeley, California 94270, USA [2] Department of Material Science and Engineering, University of California, Berkeley, California 94270, USA [3] Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94270, USA.
⁴ 1] Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, USA [2] Material Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94270, USA.

PMID: 25502099
DOI: 10.1038/nmat4148

Abstract

The Boltzmann distribution of electrons poses a fundamental barrier to lowering energy dissipation in conventional electronics, often termed as Boltzmann Tyranny. Negative capacitance in ferroelectric materials, which stems from the stored energy of a phase transition, could provide a solution, but a direct measurement of negative capacitance has so far been elusive. Here, we report the observation of negative capacitance in a thin, epitaxial ferroelectric film. When a voltage pulse is applied, the voltage across the ferroelectric capacitor is found to be decreasing with time--in exactly the opposite direction to which voltage for a regular capacitor should change. Analysis of this 'inductance'-like behaviour from a capacitor presents an unprecedented insight into the intrinsic energy profile of the ferroelectric material and could pave the way for completely new applications.