Lead zirconate titanate(Pb(Zr,Ti)$O_3$(PZT)) thin films have been prepared on Pt/$SiO_2$/Si by DC reactive sputtering using multi-target. In the present study, Ta addition effects and $PbTiO_3$ buffer layer effects on the phase formation and electrical properties of PZT thin films have been studied.
Randomly oriented polycrystalline PZT thin films were obtained at 550℃. By using $PbTiO_3$(PT) buffer layer, randomly oriented PZT thin films changed to highly (100) oriented films at 550℃ and the crystallinity of PZT thin films abruptly increased.
Structural change occurred in PZT thin films with Ta addition. With increasing Ta content, the tetragonal c/a ratio of PZT thin films decreased in terms of crystal structure and grain size increased and denser surface morphology was obtained in terms of microstructure.
Dielectric constant increased with Ta addition and hysteresis loop was slimmer. This is due to decrease of paraelectric-ferroelectric transition temperature, increase of grain size, and decrease of tetragonality. From C-V and P-E hysteresis results, asymmetric Ec due to internal bias field was found in tetragonal PZT thin films without Ta addition and with increasing Ta content, internal bias field decreased. This result is due to decrease of oxygen vacancy. Internal bias field results from defect dipolar complexes and asymmetric distribution of oxygen vacancies. Retention test results suggest that defect dipolar complexes seem to be more responsible for internal bias field. The decrease of leakage current density due to charge compensation was found in PZT thin films with Ta addition. With increasing Ta content, both initial remanant polarization and fatigue rate decreased. These changes can result from decrease of oxygen vacancy, changes of microstructure, and decrease of tetragonality.
