Resistive switching behavior of HfO2 film with different Ti doping concentrations

The effect of Ti doping concentration on the resistive switching (RS) properties of Ti-doped HfO2 samples was investigated. An x-ray photoelectron spectroscope (XPS) was used to analyze the effects of defects caused by Ti doping on RS performance. The doping of Ti into the HfO2 film reduced the formation energy of oxygen vacancies. As the Ti doping concentration increased, the enlarged ON/OFF ratio and reduced switching voltages were observed for HfO2 samples with lower Ti doping concentrations of 2.1% and 4.8%, whereas the increased currents in the high resistance state (HRS) with scattered distribution were observed for the film with a high Ti doping concentration of 7.9% due to the excess oxygen vacancies. The dependence of switching voltages and resistances on the Ti doping concentration was investigated. The reliability properties in terms of endurance and retention time were also measured. The switching mechanisms for the prepared samples were illustrated based on the oxygen vacancy filament model. The results indicated that an appropriate concentration of oxygen vacancies was required for the optimization of the RS performance.