Electrical properties of vapor-deposited yttria-stabilized zirconia thin films

The electrical properties of rf sputter-deposited thin films of ZrO2 doped with 4 mol % of Y2O3 were examined from 296 to 773 K. The films were deposited in an Ar/O2 (80/20) atmosphere at a pressure of 2 Pa under various substrate dc bias conditions (from −30 to +20 V). A Rutherford backscattering spectroscopy technique was used to determine the thickness of the films. Results showed that the deposition rate increased with applied negative dc bias ranging from 0.0486 nm/s for films produced with +20 V to 0.0972 nm/s for films produced with −30 V. Current–time measurements as a function of temperature were made in an electric field of 103 V/mm. Distinct conduction mechanisms of the ZrO2–Y2O3 films were observed from the slope change in Arrhenius plots of dc resistivity at 523 K. At low temperatures, the conduction was due to the migration of free oxygen vacancies. At temperatures above 500 K, the conduction was governed by the dissociation of oxygen vacancies trapped by the yttrium cations resulting in a higher activation energy for conduction. The effects of thermal cycling on the electrical behavior of the thin films were also investigated.