Current-voltage $\mathrm{}(I-V)\mathrm{}$ behaviors of ${\mathrm{P}\mathrm{b}(\mathrm{Z}\mathrm{r},\mathrm{}\mathrm{T}\mathrm{i})\mathrm{O}}_3$-based capacitors with ${(\mathrm{L}\mathrm{a},\mathrm{}\mathrm{S}\mathrm{r})\mathrm{C}\mathrm{o}\mathrm{O}}_3$ electrodes were studied to investigate the dominant leakage mechanism. Epitaxial ${\mathrm{}(\mathrm{L}\mathrm{a},\mathrm{S}\mathrm{r})\mathrm{CoO}}_3{/\mathrm{P}\mathrm{b}(\mathrm{Z}\mathrm{r},\mathrm{T}\mathrm{i})\mathrm{O}}_3{/(\mathrm{L}\mathrm{a},\mathrm{S}\mathrm{r})\mathrm{CoO}}_3$ 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 ${\mathrm{Ti}}^{4+}$ ion acting as the Poole-Frenkel centers.

• Received 29 June 1998

DOI:https://doi.org/10.1103/PhysRevB.59.16022