Leakage current mechanisms in lead-based thin-film ferroelectric capacitors

Current-voltage (I-V) behaviors of Pb(Zr, Ti)O-3-based capacitors with (La, Sr)CoO3 electrodes were studied to investigate the dominant leakage mechanism. Epitaxial (La,Sr)CoO3/Pb(Zr,Ti)O-3/(La,Sr)CoO3 capacitors were fabricated to simplify the analysis and eliminate any effects of granularity. The I-V characteristics were almost symmetric and temperature dependent with a positive temperature coefficient. The leakage current at low fields (<0.5 V or 10 kV/cm) shows Ohmic behavior with a slope of nearly 1 and is nonlinear at higher voltages and temperatures. Further analysis suggests that at higher fields and temperatures, bulk-limited field-enhanced thermal ionization of trapped carriers (i.e., Poole-Frenkel emission) is the controlling mechanism. The activation energies calculated for the films are in the range 0.5-0.6 eV. These energies are compatible with Ti4+ ion acting as the Poole-Frenkel centers. [S0163-1829(99)01124-8].