Spatially resolved steady-state negative capacitance

Ajay K. Yadav, Kayla X. Nguyen, Zijian Hong, Pablo García-Fernández, Pablo Aguado-Puente, Christopher T. Nelson, Sujit Das, Bhagawati Prasad, Daewoong Kwon, Suraj Cheema, Asif I. Khan, Chen-Ming Hu, Jorge Íñiguez, Javier Junquera, Long Qing Chen, David A. Muller, Ramamoorthy Ramesh, Sayeef Salahuddin*

*Corresponding author for this work

Research output: Contribution to journalLetterpeer-review

75 Scopus citations

Abstract

Negative capacitance is a newly discovered state of ferroelectric materials that holds promise for electronics applications by exploiting a region of thermodynamic space that is normally not accessible 1–14 . Although existing reports of negative capacitance substantiate the importance of this phenomenon, they have focused on its macroscale manifestation. These manifestations demonstrate possible uses of steady-state negative capacitance—for example, enhancing the capacitance of a ferroelectric–dielectric heterostructure 4,7,14 or improving the subthreshold swing of a transistor 8–12 . Yet they constitute only indirect measurements of the local state of negative capacitance in which the ferroelectric resides. Spatial mapping of this phenomenon would help its understanding at a microscopic scale and also help to achieve optimal design of devices with potential technological applications. Here we demonstrate a direct measurement of steady-state negative capacitance in a ferroelectric–dielectric heterostructure. We use electron microscopy complemented by phase-field and first-principles-based (second-principles) simulations in SrTiO 3 /PbTiO 3 superlattices to directly determine, with atomic resolution, the local regions in the ferroelectric material where a state of negative capacitance is stabilized. Simultaneous vector mapping of atomic displacements (related to a complex pattern in the polarization field), in conjunction with reconstruction of the local electric field, identify the negative capacitance regions as those with higher energy density and larger polarizability: the domain walls where the polarization is suppressed.

Original languageEnglish
Pages (from-to)468-471
Number of pages4
JournalNature
Volume565
Issue number7740
DOIs
StatePublished - 24 Jan 2019

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