Multilayer ferroelectric thin films for pyroelectric applications

High-quality multiplayer (ML) ferroelectric thin films based on erbium-doped lead titanate Pb(1−x)1.1ErxTi1−x/4O3 (PET) where <F>x=0.05</F> and Pb1.1(Zr0.58Fe0.2Nb0.2Ti0.02)O3 (PZFNT) have been processed via chemical solution deposition on textured (1 1 1)Pt/Ti/SiO2/Si substrates. The dielectric, ferroelectric and pyroelectric properties are being characterised. It is shown that the multilayer film exhibits the relaxor type behaviour found for pure PZFNT, and that its transition temperature of 310 °C at 1 kHz lies between those of PET and PZFNT. The dielectric constant of 520 also lies between those of PET and PZFNT. The ferroelectric properties are considerably improved over those of the monomorph films. An unusually high pyroelectric coefficient of approximately 620 μC m−2 K−1 was obtained from measurements of the temperature dependence of the remnant polarisation between 30 and 80 °C. The voltage and current responses measured using a modulated near IR-laser, could be improved by 2–3 orders of magnitude over those of PZFNT. The thermal time constant τT obtained is found to be 3 orders of magnitude lower than the electrical time constant τE, and indicates that the high thermal conduction rate in the substrate determines the detector responsivity. [Copyright &y& Elsevier]