Theoretical Approach to Electroresistance in Ferroelectric Tunnel Junctions

Authors

Sou-Chi Chang, Georgia Institute of Technology
Azad Naeemi, Georgia Institute of Technology
Dmitri E. Nikonov, Intel Corporation, Hillsboro, Oregon
Alexei Gruverman, University of Nebraska - LincolnFollow

Date of this Version

2017

Citation

PHYSICAL REVIEW APPLIED 7, 024005 (2017)

Comments

© 2017 American Physical Society

Abstract

In this paper, a theoretical approach comprising the nonequilibrium Green’s function method for electronic transport and the Landau-Khalatnikov equation for electric polarization dynamics is presented to describe polarization-dependent tunneling electroresistance (TER) in ferroelectric tunnel junctions. Using appropriate contact, interface, and ferroelectric parameters, the measured current-voltage characteristic curves in both inorganic (Co/BaTiO₃/La_0.67Sr_0.33MnO₃) and organic (Au/PVDF/W) ferroelectric tunnel junctions can be well described by the proposed approach. Furthermore, under this theoretical framework, the controversy of opposite TER signs observed experimentally by different groups in Co/BaTiO₃/La_0.67Sr_0.33MnO₃ systems is addressed by considering the interface termination effects using the effective contact ratio defined through the effective screening length and dielectric response at the metal-ferroelectric interfaces. Finally, our approach is extended to investigate the role of a CoOx buffer layer at the Co/BaTiO₃ interface in a ferroelectric tunnel memristor. It is shown that in order to have a significant memristor behavior not only the interface oxygen vacancies but also the CoOx layer thickness may vary with the applied bias.