Transition of resistive switching behavior for a HfO_x film induced by Ni doping

In this work, Ni-doped HfO_x films with different Ni doping concentrations were fabricated and the chemical bonding states as well as the resisistive switching characteristics were investigated. The high Ni concentration of 5.3% doping into a HfO_x sample showed the improved switching performance including enlarged ON/OFF ratio and reduced switching voltages. The switching behavior transformed from bipolar to unipolar resisistive switching due to the higher Ni doping concentration of 8.4%. The bipolar resisistive switching behavior can be attributed to the formation and recovery of oxygen vacancy filaments in the film, while the unipolar resisistive switching behavior was due to the excessive Ni dopants in the film. The C-AFM measurement was performed to observe the evolution of conductive filaments and a physical model based on oxygen vacancies or metal filaments was constructed. The reliability properties for all the samples were also demonstrated.