Preparation and properties of multilayer Pb(Zr,Ti)O3/PbTiO3 thin films for pyroelectric application

To develop a high performance pyroelectric infrared (IR) detector, Pb-1.1(Zr0.3Ti0.7)O-3/PbTiO3 (PZT/PT) multilayer thin films were deposited onto the top of a Pt/Ti/Si3N4/SiO2 membrane by a modified sol-gel process. For the comparison purpose, Pb-1.1(Zr0.3Ti0.7)O-3 (PZT) thin films were also prepared with the identical method under same conditions. X-Ray diffraction measurement revealed that the diffraction pattern of the multilayer film was the superimposition of the PZT and PT patterns. At 1 kHz, dielectric constant of 389 and 558, dielectric loss of 1.2 and 1.1% were obtained, respectively, for the PZT/PT and PZT thin films. The PZT/PT film showed a lower dielectric constant as expected and a similar dielectric loss compared with those of the PZT film, which is beneficial to use the multilayer thin films as the pyroelectric IR detecting element. Pyroelectric coefficients for the PZT/PT film and the PZT film were correspondingly 380 and 400 mu C/m(2) K. Calculated detectivity figures of merit for the PZT/PT and PZT thin films were 20.3 x 10(-6) Pa-1/2, and 18.7 x 10(-6) Pa-1/2, and values of the voltage response figures of merit were 0.038 m(2)/C and 0.028 m(2)/C, respectively. At 20 Hz, the dynamic pyroelectric voltage responsivity of 132 V/W (in rms) was obtained for the PZT/PT film and 98 V/W (in rms) for PZT film with the same element size of 240 X 360 mu m(2). High response of the multilayer thin film was ascribed to its relatively lower dielectric constant when compared to the PZT thin films. Experimental results showed the PZT/PT multilayer thin film is a good candidate material for developing high performance IR detectors. (C) 2000 Elsevier Science S.A. All rights reserved.