Resistive switching in Strontium iridate based thin films

Abstract

We report on the local electrical properties, measured by conductive atomic force microscopy, of the Iridate-based Srn+1IrnO3n+1 family of thin films, in particular by comparing the n = 1, Sr2IrO4, and the n = ∞, SrIrO3, phases. We analyze the different resistive switching behavior as a function of the pristine electronic properties of the films. We will show that, for films exhibiting insulating behavior, i.e., films of the n = 1 phase or films below 3 nm of thickness for the n = ∞ phase, hysteretic I–V curves with a sharp transition into a low resistance state (LRS), i.e. an abrupt increase of the current intensity, is detected above a well-defined threshold voltage. This suggests a resistive switching behavior associated to the jump between two resistance states that may be correlated to the activation energy, Δ, obtained by fitting the temperature dependence of the resistivity to a thermal activated Arrhenius law, ρ (T) ~ ρ0exp(−Δ/kBT). On the other hand, thicker samples of the n = ∞ phase exhibit a semimetallic character and I–V curves show progressive changes of the local resistance without a clearly defined threshold voltage. Kelvin Probe Force Microscopy based measurements confirmed that, concomitantly to the resistive switching, an evolution of the electronic states at the surface takes place that may be associated to the migration of oxygen vacancies promoted by the electrical fields under the AFM tip.