Electrical and optical properties of magnetron-sputtered Y2O3 stabilized ZrO2 thin films

The frequency dependence of both the ac conductivity and dielectric constant of thin films of ZrO2Y2O3 deposited on nickel substrates have been investigated in the frequency range 10 KHz to 10 MHz. It is shown that the total ac conductivity, sigma(omega), obeys the equation sigma(omega) = A omega(S). The frequency and temperature dependences of the parameter 's' are reported and analyzed. It appears that for ZrO2 and ZrO2-Y2O3 films, the conduction mechanism is thermally activated and both the overlap large polaron tunnelling and the correlated barrier-hopping of charge carrier over localized states fit the experimental data, depending on the Y2O3 content. The dielectric constant, (epsilon), lies in the range 22 to 38 at room temperature and decreases with increasing frequency. The sample containing 8 wt% Y2O3 displays the largest dielectric constant of 38. The loss tangent is found to be in the order of 10(-3). The refractive index shows some dispersion and a maximum value of 2.19 for the ZrO2-8 wt% Y2O3 at the wavelength of 760nm. The extinction coefficient in the order of 10(-3) is reported in the visible spectrum, which makes the films useful for some optical applications. (C) 1997 Elsevier Science Limited.