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; Bhagwati Prasad; Daewoong Kwon; Suraj Cheema; Asif I Khan; Chenming Hu; Jorge Íñiguez; Javier Junquera; Long-Qing Chen; David A Muller; Ramamoorthy Ramesh; Sayeef Salahuddin

doi:10.1038/s41586-018-0855-y

Spatially resolved steady-state negative capacitance

Nature. 2019 Jan;565(7740):468-471. doi: 10.1038/s41586-018-0855-y. Epub 2019 Jan 14.

Authors

Ajay K Yadav¹, Kayla X Nguyen², Zijian Hong³, Pablo García-Fernández⁴, Pablo Aguado-Puente⁵, Christopher T Nelson^{6

7}, Sujit Das⁷, Bhagwati Prasad⁷, Daewoong Kwon¹, Suraj Cheema⁷, Asif I Khan^{1

8}, Chenming Hu¹, Jorge Íñiguez⁹, Javier Junquera⁴, Long-Qing Chen³, David A Muller^{10

11}, Ramamoorthy Ramesh⁷, Sayeef Salahuddin¹²

Affiliations

¹ Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, USA.
² Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, USA.
³ Department of Materials Science and Engineering, Pennsylvania State University, State College, PA, USA.
⁴ Departamento de Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, Cantabria Campus Internacional, Santander, Spain.
⁵ Atomistic Simulation Centre, Queen's University Belfast, Belfast, UK.
⁶ National Center for Electron Microscopy, Lawrence Berkeley Laboratory, Berkeley, CA, USA.
⁷ Department of Materials Science and Engineering, University of California, Berkeley, CA, USA.
⁸ School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
⁹ Materials Research and Technology Department, Luxembourg Institute of Science and Technology, Esch/Alzette, Luxembourg.
¹⁰ School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA.
¹¹ Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, NY, USA.
¹² Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, USA. sayeef@berkeley.edu.

PMID: 30643207
DOI: 10.1038/s41586-018-0855-y

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 SrTiO₃/PbTiO₃ 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.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.