Metal-non metal transition in electrochromic sputtered iridium oxide films

Abstract

The low-temperature behaviour of the resistivity ϱ of electrochromic sputtered iridium oxide films (SIROF's) as a function of electrode potential (from 0.0 to 1.2 V vs SCE) is reported. In such films the Fermi level can be raised or lowered by varying the electrode potential. The ϱ(T) curves show a transition from metallic to non-metallic behaviour at about 0.45 V vs SCE. On the non-metallic side, the temperature dependence of ϱ shows a crossover from a power to an exponential law as the potential decreases. The existence of localized states in the tail of the t 2g band is postulated as a consequence of high structural disorder in SIROF's (Anderson localization). The experimental results are compared with the predictions of localization theories.