Towards the Universal Transport Properties of Metal/Insulator Granular Thin Films in the Low-Field Regime with Increasing Bias Potential or Current

Three granular systems (Fe-Al2O3, Co-Al2O3, and Ti-SiO2) had their electrical properties analyzed in the low-field regime (eV<<kBT). Even though the metals and the insulators were different, a systematic non-ohmic behavior was observed in all systems when bias or injected current were varied. The temperature dependence on the resistance was best described with the Mott variable range hopping model. It is suggested that the behavior of the electrical resistance and the electronic localization length are associated with the activation of new electronic paths between more distant grains. As these new paths configure resistances in parallel, total resistance is reduced. In the low-field regime, the resistance drop and the change in localization length seem to be universal to metal/insulator granular thin films. KeywordsElectrical Properties; Metal/Insulator Granular Film; Variable Range Hopping