Enhanced negative capacitance in La-doped Pb(Zr$_{0.4}$Ti$_{0.6}$)O$_3$ ferroelectric capacitor by tuning bias voltage pulse to induce intrinsic domain switching kinetics

Abstract: We report a remarkable enhancement of specific negative capacitance in multidomain La-doped Pb(Zr${0.4}$Ti${0.6}$)O$_3$ (PLZT) ferroelectric capacitors when bias voltage pulse profile (amplitude and timescale) induces switching of the ferroelectric domains following intrinsic switching kinetics associated with minimum energy barrier. This is because of emergence of maximum domain wall density during switching" of the domains. Domain configuration changes from such anoptimum" state if higher or lower bias voltage is applied at a much faster or slower rate. Phase-field simulation using time-dependent Ginzburg-Landau equation shows dependence of the domain wall density during switching on the bias voltage amplitude and its maximization at a specific bias voltage amplitude. The radius of curvature of the resulting polarization ($P$) versus voltage ($V$) hysteresis loop at the coercive voltage ($V_C$) also turns out to be depending on whether or not intrinsic switching kinetics is followed. All these results indicate a close correlation among the bias voltage pulse profile (amplitude and time scale), domain wall density during switching, shape of the resulting ferroelectric hysteresis loop, and the transient negative capacitance. It may have important ramifications both in the context of physics behind negative capacitance in a multidomain ferroelectric capacitor and devices being developed by exploiting its advantages.