Investigation into electrical conduction mechanisms of Pb(Zr,Ti)O3 thin-film capacitors with Pt, IrO2 and SrRuO3 top electrodes

The conduction mechanisms of Pb(Zr,Ti)O-3 (PZT) thin-film capacitors with Pt bottom electrodes and Pt, IrO2 and SrRuO3 (SRO) top electrodes were investigated. In the case of SRO top electrode prepared by pulsed laser deposition, the Schottky barrier was not formed at the interface due to the interdiffusion and the space-charge-limited current with a trap energy of 2.1 eV was dominant. On the other hand, for the Pt and IrO2 top electrodes prepared by sputtering, the capacitors showed the Schottky emission current at low electric field and the Fowler-Nordheim current at a high electric field. The Schottky barrier heights for Pt/PZT and IrO2/PZT interfaces were estimated to be 0.93 and 0.67 eV, respectively. An ultra thin alteration layer between the Pt top electrodes and PZT films seems to degrade the barrier height of the Pt/PZT interface. Furthermore, the Pt/ PZT/Pt capacitor showed negative resistance at room temperature. We concluded that the potential well formed near the top interface by band bending is the origin of this negative resistance.