Dominant conduction mechanism in NiO-based resistive memories

Abstract

The conduction characteristics of Pt/NiO/Pt resistive switching cells were investigated systematically through DC and AC conductance measurements in each of three resistance states: the initial state, the low resistance state (LRS), and the high resistance state (HRS). In the initial state, two different conduction processes are dominant, although this dominance is temperature-dependent. The activation energy (Ea) of the DC conductance was approximately 4.3 meV below 170 K. In addition to the low Ea, the frequency and temperature dependence of the AC conductance confirmed that the conduction originated from hopping between isolated sites. However, above 170 K, the Ea of the DC conductance was 330 meV, and this conductance was independent of frequency at low frequencies. The dominant conduction process above 170 K was found to be band conduction from analysis of the AC conductance. The resistance in the LRS varied linearly with temperature and was almost independent of frequency, thus representing the characteristics of metallic band conduction of conductive filaments. In the HRS, the DC conductance exhibited an Ea of 16 meV, which was higher than that in the initial state (4.3 meV), thus indicating that the dominant conduction mechanism in the HRS is different to the mechanism in the initial state. From discussions based on a filament model, it was concluded that filament conduction is dominant in the HRS. As a result, it is proposed that the resistive switching originates from changes in the conduction properties of the filaments themselves rather than from their rupture and formation.