Enhanced-response pyroelectric heterostructures

We have observed enhanced pyroelectric responses in sub-100 nm, epitaxial Pb–Zr–Ti–O films contacted with conducting perovskite oxide top and bottom electrodes. These enhancements are obtained in capacitors where the bottom electrode is processed under reducing conditions. This leads to an asymmetric, temperature-dependent internal electric field that is produced within the ferroelectric capacitor and manifests itself as a strongly shifted ferroelectric hysteresis loop. Because the shifted coercive voltage lies near the unbiased operating point, the pyroelectric film has a large value of dP/dE. The product (dP/dE)/(dE/dT) gives rise to an enhanced pyroelectric response. Our data show that a 10–30 times increase in the pyroelectric response can be obtained over symmetric devices, with a concomitant improvement of the sensing figure-of-merit by three times.