Constant-phase-element (CPE) modeling of ferroelectric random-access memory lead zirconate-titanate (PZT) capacitors

Several commercial high density ferroelectric random access memory (FeRAM) devices utilize stacks of submicron lead zirconate-titanate (PZT) capacitors. The low-field electrical characteristics of these capacitors display a specific frequency dependence which is best represented by a constant phase element (CPE) in the equivalent circuit diagram. The microscopic origin of such CPEs in the general literature is still of some debate, often being attributed to fractal dimensionality of the capacitor, near-electrode gradients in the dielectric, fringing fields near the electrode perimeter or, more generally, a distribution of relaxation times. We discuss these possibilities.