Metal-ferroelectric-metal structures with Schottky contacts. II. Analysis of the experimental current-voltage and capacitance-voltage characteristics of Pb(Zr,Ti)O3 thin films

A modified model of metal-semiconductor contacts is applied to analyze the capacitance-voltage and current-voltage characteristics of metal-ferroelectric-metal structures. The ferroelectric polarization is considered as a sheet of surface charge situated at a fixed distance from the interface. The presumable high concentration of structural defects acting as active electric traps is taken into account by introducing a deep acceptorlike level. The model is applied on a set of metal-Pb(Zr,Ti)O3-metal samples with different Zr∕Ti ratios, deposited by different methods, and having different thicknesses, electrode materials, and electrode areas. Values around 1018cm−3 were estimated for the hole concentration from capacitance-voltage measurements. The space-charge density near the electrode, estimated from current-voltage measurements, is in the 1020–1021cm−3 range. The total thickness of the interface layer ranges from 3to35nm, depending on the Zr∕Ti ratio, on the shape of the hysteresis loop, and on the electrode material. The simulated I-V characteristics is fitted to the experimental one using the potential barrier and Richardson’s constant as parameters. The potential barrier is determined to be in the 1.09–1.37eV range and Richardson’s constant is 520Acm−2K−2.