Preparation and characterization of Ppy/Al2O3/Al used as a solid-state capacitor

The characteristics of a solid-state capacitor based on Ppy (polypyrrole)/Al2O3/Al prepared by the constant-current method are investigated. The surface composition of aluminum (Al) foil analyzed to by electron spectroscopy for chemical analysis (ESCA) is found to be AlO2− when the native oxide on the Al foil is etched by 0.1 M NaOH. Three stages are defined from the relationship between the potential and the electrolysis time in simultaneously preparing the dielectric layer (Al2O3) and the conducting polymer (Ppy) on Al foil etched with 0.1 M NaOH. The experimental results indicate that only stage one, i.e. the formation of Al2O3, occurs in the preparation of Ppy/Al2O3/Al at a current density greater than 0.9 mA cm−2. A higher concentration of pyrrole enhances the nucleation of Ppy within the pores of Al2O3 such that the period of the first stage decrease and the second stage of the propagation of Ppy is increased. The leakage current of Ppy/Al2O3/Al rises from 0.009 to 0.405 μA cm−2 with increase in the concentration of pyrrole in preparing Ppy/Al2O3/Al from 0.05 to 0.15 M. Raising the cut-off potential for preparing Ppy/Al2O3/Al from 20 to 60 V increases the thickness of Al2O3 and lowers the capacity of Ppy/Al2O3/Al from 478.5 to 174.2 nF cm−2.