Effect of Ni-doped on switching mechanisms and characteristics of ZnO-based memristor: Experimental and first-principles investigations

Abstract

In this paper, we explore the impact of Ni doping on the resistive switching (RS) performance of ZnO-based resistive random access memory (RRAM). The Ti/ZnO: Ni/ITO resistive memory exhibits a reduced and less discrete forming voltage (Vforming) and set voltage (Vset), along with a more stable high resistance state (HRS). The doping does not change the conductivity mechanism of the device. The observed outcomes can be attributed to the influence of Ni doping on the generation and breakage of the oxygen vacancy conductive filaments (CF) in the vicinity. Using First-Principles calculations, we calculated the formation energy of oxygen vacancies (Vos), the band structure, the density of states (DOS), charge density, and electronic properties of the doped ZnO cell. The oxygen vacancy formation energy (Efv) is significantly lower in the Ni-doped ZnO cell, which is associated with lower Vforming and Vset. And it allows for less randomness in the generation of CF, which improves the stability of the HRS. The band structure shows that Ni doping can add an additional band at the Fermi energy level of ZnO, corresponding to the defect states in the density of states. The improved storage capacity of Ni-doped ZnO devices has been experimentally demonstrated.