Oxygen vacancy modulation and enhanced switching behavior in HfO_x film induced by Al doping effect

The effect of Al doping concentration on resistive switching characteristics of Pt/Al-doped HfO_x/Cu structures was investigated. According to the X-ray photoelectron spectroscopy (XPS) analysis and the first-principle calculation, the Al doping introduced more oxygen vacancies in HfO_x film and these oxygen vacancies can be easily generated along Al dopants. Significant enhancement in resistive switching behaviors was achieved for 6.8% Al-doped HfO_x film in terms of ON/OFF ratio, switching voltages and uniformity, whereas the higher Al doping concentration of 9.4% caused excess oxygen vacancies in the film, resulting in the degeneration of switching performance. A schematic diagram based on the formation and rupture of oxygen vacancy filaments was proposed to illustrate the distinct switching behaviors of HfO_x and Al-doped HfO_x samples. The results indicated that the concentration and distribution of oxygen vacancies played an important role on resistive switching behavior. The reliability properties for the prepared HfO_x samples were also investigated. This work might provide a guidance for the further optimization of HfO_x-based memory.