rf planar magnetron sputtering and characterization of ferroelectric Pb(Zr,Ti)O₃ films

Abstract

Ferroelectric films of lead zirconate titanate (PZT) have been fabricated by rf planar magnetron sputtering. Films having a resistivity >10⁶ Ωcm and a dielectric constant >800 at 300 K have been achieved using 100% oxygen as a sputtering medium, 10% excess PbO added to the target, and appropriate post-deposition annealing. The sputtering rate is in the range 0.2-1.0 µ m/h and varies with sputtering pressure and substrate temperature. Post-deposition annealing affects both crystallinity and grain size, but incipient crystallization formed only in as-grown films deposited at substrate temperatures >400° C is essential for this process to be effective. A clear ferroelectric transition is observed at 350° C, while the activation energy for dc conductivity of around 0.8 eV is consistent with bulk properties of PZT. The spontaneous polarization and coercive field measured from ferroelectric hysteresis loops is 20.75 µ C/cm² and 10 kV/cm, respectively. The optical transmittance of the films is determined by a Pb-Pb charge transfer band near 400 nm and this is a sensitive test of film stoichiometry.