Electric Conduction Mechanisms Study within Zr Doped Mn₃O₄ Hausmannite Thin Films through an Oxidation Process in Air

Abstract

In this work further optical and electrical investigations of pure and Zr doped Mn 3 O 4 (from 0 up to 20 at.%) thin films as a function of frequency. First, the refractive index, the extinction coefficient and the dielectric constants in terms of Zr content are reached from transmittance and reflectance data. The dispersion of the refractive index is discussed by means of Cauchy model and Wemple and DiDomenico single oscillator models. By exploiting these results, it was possible to estimate the plasma pulse ω p , the relaxation time τ and the dielectric constant ε ∞ . Second, we have performed original ac and dc conductivity studies inspired from Jonscher model and Arrhenius law. These studies helped establishing significant correlation between temperature, activation energy and Zr content. From the spectroscopy impedance analysis, we investigated the frequency relaxation phenomenon and hopping mechanisms of such thin films. Moreover, a special emphasis has been putted on the effect of the oxidation in air of hausmannite thin films to form Mn 2 O 3 ones at 350°C. This intrigue phenomenon which occurred at such temperature is discussed along with this electrical study. Finally, all results have been discussed in terms of the thermal activation energies which were determined with two methods for both undoped and Zr doped Mn 3 O 4 thin films in two temperature ranges.