Preparation and properties of multilayer Pb(Zr,Ti)O-3/PbTiO3 thin films for pyroelectric application

To develop a high performance pyroelectric infrared (IR) detector, Pb-1.1(Z r0.3Ti0.7)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 prepar ed with the identical method under same conditions. X-Ray diffraction measu rement 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 dielect ric 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 th e 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. Calc ulated 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 r esponse 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 th in film was ascribed to its relatively lower dielectric constant when compa red to the PZT thin films. Experimental results showed the PZT/PT multilaye r thin film is a good candidate material for developing high performance IR detectors. (C) 2000 Elsevier Science S.A. All rights reserved.