Dielectric properties of Cd0.6Zn0.4 thin films

Cd0.6Zn0.4Te thin films of different thicknesses were prepared by the thermal evaporation technique onto well-cleaned Coming glass substrates. The dielectric properties of Al/Cd0.6Zn0.4Te/Al sandwich structures were studied in the frequency range 50 Hz-4 MHz and in the temperature range 300-420 K. The effect of thickness on the net dielectric constant was studied in detail. The bulk dielectric constant was calculated as 13.5, which is consistent with the value of 11.5-8.2 measured at I MHz for the films of different thickness varying between 120 and 850 nm. The relaxation phenomenon present in the films is due to the presence of grains and grain boundaries across the film thickness. The relaxation times decrease with increasing measuring temperatures, suggesting that the net relaxation phenomenon is associated with the charge carrier transport mechanism. The grain boundary activation energies, calculated from the spectroscopic plot, vary between 0.61 and 0.53 eV. The variation of conductivity as a function of temperature and frequency reveals non-adiabatic hopping of charge carriers between impurity sites/localized states and the activation energies are found to vary between 0.28 and 0.11 eV. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.