A multi-level memristor based on atomic layer deposition of iron oxide

This work reports the fabrication of memristive devices based on iron oxide (Fe2O3) thin films grown by atomic layer deposition using ferrocene as iron precursor and ozone as oxidant. Excellent control of atomic layer deposition (ALD) is achieved by using an experimental procedure based on a sequence of micro-pulses, which provides long residence time and homogeneous diffusion of precursors, allowing ALD of thin films with smooth morphology and crystallinity increasing with layer thickness at temperatures as low as 250°C. The resistive switching of symmetric Pt/Fe2O3/Pt thin film devices exhibit bipolar mode with good stability and endurance. Multi-level switching is achieved via current and voltage control. It is proved that the ON state regime can be tuned by changing the current compliance while the OFF state can be changed to intermediate levels by decreasing the maximum voltage during RESET. The structural analysis of the switched oxide layer reveal the presence of nano-sized crystalline domains corresponding to different iron oxide phases, suggesting that Joule heating effects during I-V cycling are responsible for a crystallization process of the pristine amorphous layer.