Imprint in ferroelectric capacitors

We show that voltage offsets in the polarization-voltage characteristics of Pb(Zr, Ti)O3 capacitors can lead to imprint in ferroelectric memory devices. The thermal-induced voltage shifts (internal bias field) are in part attributed to the role of oxygen vacancy-related defect dipoles throughout the film. In support of this, it is found that donor doping at the Ti(Zr) sites reduces the thermally-induced voltage shifts. The stress-induced voltage shifts are found to be dependent on the Zr/Ti cation ratio. This compositional dependence is explained by considering the role of deep bulk Ti3+ centers and/or a compositional dependent oxygen vacancy density.