The interface screening model as origin of imprint in PbZrxTi1−xO3 thin films. I. Dopant, illumination, and bias dependence

Abstract

Comprehensive imprint measurements on ${\mathrm{PbZr}}_x{\mathrm{Ti}}_{\text{1−x}}{\mathrm{O}}_3$ (PZT) thin films were carried out. Different models, which were proposed in literature to explain imprint in ferroelectric thin films or a similar aging effect (internal bias) in ferroelectric bulk material, are reviewed. Discrepancies between the experimental results obtained on the PZT films in this work and the prediction of the literature models indicate that these models do not describe the dominant imprint mechanism in PZT thin films. Hence, in this work a model is proposed which suggests imprint to be caused by a strong electric field within a thin surface layer in which the ferroelectric polarization is smaller or even absent compared to the bulk of the film. With the proposed imprint model the influence of important experimental parameters like dopant, illumination, and bias dependence can be qualitatively explained.