Impedance fluctuations in epitaxial PZT films

• We report on measurements of impedance of Au/PZT/La0.67Sr0.33MnO3/Pt80Ir20 thin film capacitors performed in the time domain. Ferroelectric PZT films pulsed laser deposited on bulk polycrystalline Pt80Ir20 substrates demonstrate good ferroelectric properties: dielectric permittivity epsilon' = 880 and loss tandelta = 0.039 at 1 kHz, remnant polarization as high as 20 muC/cm(2), induced polarization of 40 muC/cm(3) at 380 kV/cm, and coercive field of 52.5 kV/cm. Resistivity of PZT film at coercive field was found to be 3.10(12) Omega.cm. Instantaneous C-V and I-V characteristics have been recorded to study the relaxation of polarization. Transient current exhibits non-Debye type relaxation, which has been nicely fitted to Curie-von Schweindler law j = j(leak) + j(o) (t/1sec)(-n) with an exponent nsimilar to0.8 while the power law C proportional to f(-0.1) has been found in frequency dispersion of the capacitance. Impedance fluctuation spectrum in the true leakage and resistance degradation regimes was found to follow 1/f(1.5) dependence. Close to breakdown field voltage fluctuations in ferroelectric capacitor increase, become non-steady randomly spike-shaped.

Nyckelord

pulsed laser deposition

thin ferroelectric PZT films

relaxation of polarization

impedance fluctuations

noise

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