Simultaneous Measurement of the In- and Across-Plane Ionic Conductivity of YSZ Thin Films

Abstract

Yttriastabilized zirconia (YSZ) thin films of 20 to 90 nmthickness were prepared by pulsed laser deposition (PLD) on siliconsubstrates with a native silica layer. The high dc resistanceof the silica interlayer causes strongly frequency dependent current linesbetween two stripe electrodes on the YSZ layer. This allowsdetermination of the in- and across-plane conductivity of the YSZfilm from a single impedance spectrum. The high frequency partof the impedance spectra corresponds to an across-plane measurement geometrywhile the low frequency part is governed by in-plane currentflow. It is shown that the measured in-plane conductivity isabout one order of magnitude lower than the across-plane bulkconductivity. This anisotropy is attributed to the blocking effect ofgrain boundaries in the columnar structured YSZ films. The activationenergies of across-plane ionic conductivity (~0.8 eV) are lower thanthose of in-plane conduction (~1 eV). ©2012 The Electrochemical Society