Properties of Sol–Gel Derived (Polyvinylidene Fluoride/Lead Titanate) Pyroelectric Bilayer Thin Films

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Ferroelectric polymer/ceramic bilayer thin films composed of polar $\beta$-phase polyvi-nylidene fluoride (PVDF) and 1-$\mu$m-thick polycrystalline lead titanate (PbTiO3) thin films were prepared, using a sol–gel method. The influence of various processing parameters on the characteristics of PVDF/PbTiO3 thin films was studied by varying the thickness of PVDF thin films (100–580 nm). The results show that the surface of the obtained PVDF film was smooth with less lower porosity above the PbTiO3 film, enabling a significant decrease in the leakage current of bilayer thin films. Although the coercive field ($E_{\text{c}}$), remanent polarization ($P_{\text{r}}$) and pyroelectric constant ($p$) of bilayer thin films decreased with the increase of PVDF thin film thickness, the deposition of PVDF thin films onto the PbTiO3 films caused the leakage current ($J$) measured at 40 kV/cm to decrease from $1.57 \times 10^{-6}$ A/cm2 to $3.86 \times 10^{-7}$ A/cm2 as well as the relative dielectric constant ($\epsilon_{\text{r}}$) from 63 to 20. The figures of merit ($F_{\text{V}}$ and $F_{\text{m}}$) due to relative low-dielectric constant ($\epsilon_{\text{r}}$) revealed that good infrared responses of bilayer thin films can be utilized in their application to detectors.
2003-01-15