Dielectric relaxation in polycrystalline thin films of In2Te3

Measurements of the dielectric properties of stoichiometric In2Te3 thin fil ms prepared by thermal evaporation technique onto clean glass substrates us ing ohmic aluminum electrodes are carried out in the frequency range 10(2)- 10(5) Hz and within the temperature range 300-400 K. The frequency dependen ce of the impedance spectra plotted in the complex plane shows semicircles. The system could be represented by an equivalent circuit of bulk resistanc e in series with a parallel surface resistance-capacitance combination. The Cole-Cole types have been used to determine the molecular relaxation time, tau. The temperature dependence of tau is expressed by thermally activated process. AC conductivity sigma (AC)(omega) is found to vary as omega (n) w ith the index 0.65 less than or equal to n less than or equal to 0.83, and it decreases with increasing the temperature, indicating a dominant hopping process at the temperature range 300-400 K. From the temperature dependenc e of AC conductivity, free carrier conduction with activation energy varies from 0.05 to 0.008 eV are observed in the frequency range 10(2)-10(5) Hz a nd within the temperature range 300-400 K. Capacitance and loss tangent are found to decrease with increasing frequency and increasing with increasing temperature. Such characteristics are found to be in good qualitative agre ement with existing equivalent circuit model assuming ohmic contacts. (C) 2 001 Elsevier Science B.V. All rights reserved.