Effect of dopants on ferroelectric and piezoelectric properties of lead zirconate titanate thin films on Si substrates

Lead zirconate titanate Pb(Zr0.52Ti0.48)O3 (undoped PZT) and doped PZT thin films with thickness of about 500 nm were grown on Pt/Ti/SiO2/Si substrates by pulsed laser deposition (PLD). In this study, 1.0 mol% Nb-doping (at Zr/Ti site) as donor, 1.0 mol% Fe-doping (at Zr/Ti) as acceptor and 10 mol% Ba-doping (at Pb site) as isovalence were used. The effects of the introduction of these dopants on the ferroelectric and piezoelectric properties were investigated and compared to the undoped PZT film. A noticeable improvement of the dielectric constant (ε) and effective piezoelectric coefficient (d33,f) are obtained. The maximum values of these parameters vary from 1280 and 126 pm/V for undoped PZT film to 1520 and 164 pm/V for Nb-doped PZT film. The largest remnant polarization (Pr) and coercive field (Ec) are obtained for Fe-doped PZT film, equal to 22.6 µC/cm2 and 35.3 kV/cm, as compared to 17.3 µC/cm2 and 31.2 kV/cm respectively for undoped PZT film. The Ba-doping decreases the dielectric constant but enhances the breakdown field of the film, reaching 800 kV/cm while it was only 660 kV/cm for undoped PZT film. The crystalline structure of Ba-doped film has a dominating (110) orientation instead of (100) in case of undoped, Nb-, and Fe-doped PZT films. The obtained results are important for the applications of doped PZT films in piezoMEMS devices.