Imprint in ferroelectric materials due to space charges: A theoretical analysis

Imprint is a degradation mechanism in ferroelectrics that results in the displacement of the polarization hysteresis loop along the electric field axis. We develop a model using a nonlinear thermodynamic analysis coupled with electrostatics to show that such internal voltage offsets can originate from asymmetrically distributed trapped space charges. The electrostatic interactions are established through a built-in polarization due to the space charges and the spontaneous polarization. Numerical results for Ba0.8Sr0.2TiO3 show that the maximum electric field offset does not necessarily occur due to charges trapped near the electrodes. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3222871]