Enhanced pyroelectric coefficient of antiferroelectric-ferroelectric bilayer thin films

In this study, the pyroelectric coefficient and the figure of merit (FOM) of the ferroelectric PbZr0.3Ti0.7O3 (PZT 30/70) thin films were found to be greatly enhanced by introducing a thin antiferroelectric PbZr0.95Ti0.05O3 (PZT 95/05) layer underneath the ferroelectric film and thus creating a bi-layer structure on platinised silicon substrates. The film properties were investigated as a function of the ferroelectric layer thickness when the thickness of antiferroelectric layer remained unchanged. The highest pyroelectric coefficient of 1 mm thick PZT 30/70 film was 3.18 x10-4 Cm-2K-1. However, the highest pyroelectric coefficient for 1 mm thick bi-layer film was 3.5 x10-4 Cm-2K-1 or 2.5 x10-4 Cm-2K-1 for only 280 nm thick bi-layer film. The enhancement of pyroelectric coefficient suggests switching of antiferroelectric (AF) into ferroelectric (FE) phase during poling and following stabilization of FE phase at room temperature. The reduction of dielectric constant in bi-layer films after poling, compared to pure PZT 30/70, showed a FOM of 2.94 x10-5 Pa-0.5 which is the double of the FOM for pure PZT 30/70 films of similar thickness (1.45 x10-5 Pa-0.5).