Impact of the surface/interface on the ionic conductivity of thin film Gd-doped CeO2

Literature reports suggest that the surface and interface regions of thin film Gd-doped CeO2 (GDC) may act as highly conductive paths for ionic transport (Lee et al., 2009; Huang et al., 2006)[1,2]. However, no study has been published that directly tests the impact of the surface and interface on the total ionic conductivity of single crystal thin film GDC. In this study, single crystal GDC films have been grown to thicknesses varying from 20 to 500 nm and their conductivities have been measured in the 500–700 °C temperature range. Decreasing conductivity with decreasing film thickness was observed. Analysis of the conductivity data is consistent with the presence of an approximately 50 nm layer of less conductive material in every film. This study concludes that the surface and interface regions of thin film GDC are less conductive than the bulk single crystal regions, rather than being highly conductive paths.

Research Highlights
► The impact of film interface on the ionic conductivity of GDC films was studied.
► Conductivity measurements were made on single crystal films 20-500 nm thick.
► Decreasing conductivity with decreasing film thickness was observed.
► Analysis showed an approximately 50 nm layer of reduced conductivity in every film.
► Interface region of the GDC film is less conductive than bulk single crystal region.