Dielectric relaxation properties, and AC conductivity of Erbium(III)-Tris(8-hydroxyquinolinato) nanostructured films

Abstract

Thin films of Erbium (III)-Tris (8-hydroxyquinolinato (ErQ3) were accomplished by thermal evaporating procedure. The thermal stability of ErQ3 powder was studied by the differential scanning calorimeter (DSC). The SEM image of ErQ3 thin film revealed that the surface morphology of ErQ3 is composed from several of islands structure, meanwhile each island look like algae-shape. The variation of the dielectric real and imaginary parameters versus temperature and frequency were discussed. The real dielectric constant and dielectric loss show a remarkable dependence on the frequency and temperature. The activation energy of the relaxation process (ΔE) was found to be 0.428 eV. In addition, the density of localized states at Fermi levels N(Ef) was estimated to be 1.33×1018eV−1cm−3. AC conductivity at various frequencies and temperatures was investigated. At high frequency regime, the AC conductivity behavior was explained by Jonscher formalism. The charge transport mechanism was found to be controlled by the barrier hopping model (CBH). The decrease of the potential barrier height (Wm) as temperature increases unveils the growing of diffusion charges as the temperature increases. The decrease of the activation energy of the AC conductivity (ΔEAc) as the frequency increases confirms the effect of the applied frequency in the enhancement of the eletrons hopping between the two nieghoburing sites. Overall, the relatively small value of the potential barrier height (Wm) and the extensive localized electronic states encourages the utilizing of ErQ3 in designing the solar cell units.