AC CONDUCTIVITY AND DIELECTRIC PROPERTIES OF Al2O3 THIN FILMS

Abstract

Al2O3 thin films of different thicknesses were prepared onto clean glass substrates using ohmic aluminum electrodes. Their dielectric properties and ac conductivity have been investigated in the frequency range 0.1-100KHz and within the temperature range 100-400K. Oxide-layer thicknesses of the films range between 50-1550 angstrom. The dielectric constant epsilon(1). was found to decrease with increasing frequency and increase with temperature in the given intervals. Only ac losses have been investigated due to the smallness of dc losses. The ac conductivity satisfies the power law omega(s). Here the s parameter is in the vicinity of 0.8 and it decreases with increasing temperature. This behaviour of s can comply with CBH model. The activation energy values calculated from ac conductivity and dielectric loss factor measurements are in good agreement with each other. The obtained values agree with the model of hopping of charge carriers by thermal activation between two sites having a coulombic potential well. Film thickness dependence of Temperature Coefficient of Capacitance (TCC) and Temperature Coefficient of Permittivity (TCP) of the Al2O3 thin films were also determined.