Polarization Reversal of (111)- and (100)/(001)-Oriented Pb(Zr,Ti)O₃ Thin Film Capacitors with SrRuO₃ and IrO₂ Thin Film Top Electrodes

Abstract

(111)- and (100)/(001)-oriented Pb(Zr,Ti)O₃ (PZT) thin films were deposited using a chemical-solution deposition (CSD) method. For the top electrodes, IrO₂ and SrRuO₃ (SRO) thin films were deposited by sputtering. The ferroelectric properties and crystal structure of the (111)- and (100)/(001)-oriented PZT thin-film capacitors were evaluated. The switchable polarization (Qsw) of a (100)/(001)-oriented PZT capacitor with an SRO top electrode was lower than that with an IrO₂ top electrode. The opposite trend in Qsw was observed with IrO₂ and SRO top electrodes in (111)-oriented PZT capacitors. With continuous switching cycles, the Qsw of a (100)/(001)-oriented PZT capacitor with IrO₂ increased continuously with an increasing number of cycles. However, there was no increase in Qsw in a (100)/(001)-oriented PZT capacitor with SRO. Transmission electron microscopy (TEM) observation showed a local epitaxial-like interface between the SRO and PZT in both the (111) and (100)/(001) orientation. However, a heterostructure was observed in the IrO₂/PZT interface in both orientations. TEM also showed the existence of several 90° domains in the (100)/(001)-oriented PZT films. At the SRO/PZT(100)/(001) interface, this local epitaxial-like interface seemed to block the movement of the 90° domain wall. As a result, the Qsw was lower in a (100)/(001)-oriented PZT capacitor with SRO than that with IrO₂.