Fig. 4. Demonstration of transient negative capacitance.
a Voltage transients of a H-NNO capacitor (1.1 nF at 1 kHz) with a series resistor R = 702 kΩ. Vs is the applied voltage and Vf the voltage across the ferroelectric. Inset is the circuit of the pulse measurement. b, c The close-up view of NDC regions corresponding to (a). d Charge density as a function of Vf. The negative slope indicates the differential negative capacitance. Inset is the close-up view of the NC region. e The negative differential capacitance region with different series resistors. f Schematic illustration of switching of spontaneous polarization during a square voltage pulse.