Nonlinear Electron Transport and Effects of Resistive Switching in Iron Nanoparticle Metal Oxide/Metal Composites

Abstract

Voltammetric methods are used to study longitudinal electron transport and the effects of resistive switching in films of nanoparticle metal oxide (Fe/FeO_x)/metal composites grown by magnetron sputtering (in an argon atmosphere) and the ensuing iron oxidation. Formation of iron nanograins and intergrain oxide is controlled using the methods of electron microscopy, Raman spectroscopy, and X-ray diffraction. Analysis of voltammetric characteristics of the composite shows the linear ohmic mode of electron transport at low voltages and the nonlinear electron transport mode at high voltages. The resistive switching of the composite from the low conductivity state (LRS) into the high conductivity state (HRS) accompanied by formation of magnetite Fe₃O₄ regions in the intergrain FeO_x oxide characteristic for memristor materials is registered at an increase in voltage. At a further increase in voltage, the reverse process is registered: the switching of the studied film from the high conductivity state in the low conductivity state due to oxidation of intergrain magnetite to maghemite. As the breakdown voltage is registered on the surface of such a composite, a system of oriented elongated ghematite nanoparticles with the average diameter of 45 nm and length of up to 2 μm is formed.