Negative Capacitance from the Inhomogenous Stray Field in a Ferroelectric–Dielectric Structure

The phenomenological Landau–Ginzburg–Devonshire model provides a fundamental background for an understanding of the peculiar charge–voltage behavior of ferroelectric (FE) materials. However, the model cannot explain the polarization behavior of multidomain FE materials. The experimentally observed negative capacitance (NC) effect, which is interpreted as an emergence of the Landau barrier effect, involves particular conceptual difficulty. This work provides a new conceptual framework to explain the quasi‐static NC effect based on the energy formula for a stacked dielectric/ferroelectric (DE/FE) layer structure with the multidomain configuration with arbitrary shape. The presence of such domain configuration causes the energy–displacement curve of the inhomogenous Helmholtz energy term to have negative curvature. This is caused by the stray field between the neighboring domains. The model can be further extended to the DE/FE system with polycrystalline FE grains using the advanced phase‐field analysis. It is determined that the NC effect from the stray field is a universal phenomenon. These models provide quantitative explanations for the previously reported short‐pulse measurement results for various DE/FE material systems, which have lacked accurate interpretations. An inhomogeneous stray energy (ISE) model is suggested to explain the quasi‐static negative capacitance (NC) effect in a dielectric/ferroelectric structure with multidomain configuration. This model shows that the NC effect is attributed to the inhomogeneous energy in the structure. The figure shows: (a‐b) Displacement field‐Helmholtz energy relationships in the Landau‐Ginzburg‐Devonshire model and ISE model (c) inhomogeneous potential profiles in the structure.