Thickness effects on imprint in chemical-solution-derived (Pb, La)(Zr, Ti)O3 thin films

Abstract

The film thickness-dependent imprinting behavior (voltage shift) of (Pb, La)(Zr, Ti)O3 capacitors was evaluated by a thermal stress process under a remanence bias. The remanent polarization (Pr) was found to be almost independent of the film thickness whereas in the 50–300 nm range the relative dielectric constant (εr) increased linearly with the square root of the film thickness. It was found that the voltage shift, which was attributed to the accumulation of charged defects near the electrode interface, also increased linearly with increasing film thickness. In addition, the charge accumulated thickness varied with the square root of the film thickness. This was established from a simple assumption that the level of charge accumulation is determined by the product of the total amount of charged defects (total film thickness×charged defect density) and the internal field that is generated by the Pr. Therefore, the imprint is much more a bulk-related degradation phenomenon compared to the fatigue.