Metal-ferroelectric-metal structures with Schottky contacts. II. Analysis of the experimental current-voltage and capacitance-voltage characteristics of Pb (Zr,Ti) O 3 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 ZrTi ratios, deposited by different methods, and having different thicknesses, electrode materials, and electrode areas. Values around 1018 cm-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 - 1021 cm-3 range. The total thickness of the interface layer ranges from 3 to 35 nm, depending on the ZrTi 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 1.09-1.37 eV range and Richardson's constant is 520 A cm-2 K-2. © 2005 American Institute of Physics.