Theoretical Approach to Electroresistance in Ferroelectric Tunnel Junctions

  • Authors:
    Sou-Chi Chang (Georgia Tech), Azad J. Naeemi (Georgia Tech), Dmitri Nikonov (Intel), Alexei Gruverman (U Nebraska/Lincoln)
    Publication ID:
    Publication Type:
    Received Date:
    Last Edit Date:
    2624.001 (Georgia Institute of Technology)


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=La0.67Sr0.33MnO3) 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=La0.67Sr0.33MnO3 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.

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