Microstructural and electrical properties of ferroelectric capacitors with Pt/RuO₂ hybrid electrodes

Thin films of Pb(Zr_0.53Ti_0.47)O₃ (PZT) grown in our laboratory on RuO₂ electrodes by the sol-gel process are characterized by high leakage currents and by the presence of a pyrochlore-type second phase. We have used a thin Pt interlayer between the PZT film and RuO₂ bottom electrode to produce RuO₂/PZT/100 angstroms Pt/RuO₂/SiO₂/Si capacitor structures. It is found that use of such a Pt interlayer significantly reduces or eliminates the second phase in the PZT films, and lowers their leakage currents by more than four orders of magnitude. At the same time, the excellent resistance to polarization fatigue characteristic of the RuO₂/PZT/RuO₂ capacitors is maintained. The microstructures of PZT films grown on RuO₂ electrodes with and without the 100 angstroms Pt interlayer are compared. In addition, the voltage, temperature, and polarity dependence of the leakage current in these samples was measured. The data suggest that leakage current in these samples is most likely Schottky emission controlled. The barrier heights are determined to be about 0.80 and 0.73 eV for the top and bottom interfaces, respectively.