Understanding negative capacitance dynamics in ferroelectric capacitors

We investigate negative capacitance transients-the time period during ferroelectric switching when the voltage across a ferroelectric changes in a direction opposite to that of the charge-by constructing a simple series network of an isolated single crystalline ferroelectric capacitor and an external resistor. A study of negative capacitance dynamics in such a circuit reveals that the time scale of this phenomenon is controlled by the external resistor rather than by the material dependent intrinsic speeds. As a canonical approach for directly measuring ferroelectric negative capacitance, these experiments could guide the efforts to stabilize negative capacitance in a transistor structure for sub-60 mV/decade subthreshold characteristics as well as help assess negative capacitance response speed at technologically relevant dimensions. © 2015 IEEE.