The resistive switching characteristics of Ni-doped HfO_x film and its application as a synapse

The effect of Ni doping concentration on resistive switching characteristics of Au/HfO_x:Ni/Pt structure was investigated, and the 3.1% Ni-doped HfO_x film was used to imitate the function of biological synapse. From the X-ray absorption near edge structure analysis, the forms and the local electronic structure of Ni atoms in the HfO_x films with different Ni doping concentrations were investigated. According to the X-ray photoelectron spectroscopy analysis, the Ni doping introduced more oxygen vacancies in HfO_x films. Gradual Reset process and concentrated distribution of resistive switching parameters were achieved for 3.1% Ni-doped HfO_x films, which could be used to emulate the “learning” and “forgetting” function of the biological synapse. Multiple resistance levels can be observed in the continuously pulse number under identical pulse width of positive or negative voltage pulses. Moreover, the application of pulse-train operation scheme is an effective method to control analog synaptic devices during the Reset process, which can contribute to understand the nature of the conductive nano-filament evolution.