On the Quasi-Static Negative Capacitance in HfO₂ -based Ferroelectrics

Negative capacitance stabilized in HfO₂-based ferroelectric films offers a promising solution for low power-dissipation nanoscale electronics, however, its physical picture is still under intensive debate.Herein, the ferroelectric HfO₂/dielectric double layer system was modeled based on the Landau- Devonshire and Landau-Khalatnikov equations.Results show that the conventional quasi-static negative capacitance theory, which is rooted in the zero-field Gibbs free energy landscape and the quasi-static polarization-voltage curve, cannot capture the true polarization-voltage trajectory during the dynamic switching process.The negative capacitance observed in the ferroelectric HfO₂/dielectric system depends strongly on the evolution of the voltage dived by the dielectric layer and has a transient nature, which is at odds with the prediction of the quasi-static negative capacitance theory.Moreover, the emergence of hysteresis is ascribed to the thermal dissipation related to the damping parameter in the Landau- Khalatnikov equation, and it cannot be fully suppressed by the capacitance matching scenario.The thermal dissipation induced by the damping parameter is hugely enhanced with increasing frequency, which makes the high-frequency application of negative capacitance field-effect transistor rather impossible.This study provides an in-depth understanding on the underlying mechanism of the negative capacitance effect found in the HfO₂-related materials.