Appearance of quantum point contact in Pt/NiO/Pt resistive switching cells

A resistive switching (RS) phenomenon, namely reversible transitions between the low and high resistance states after forming process, is caused by the formation and rupture of a conductive filament. We confirmed that conductive filaments including a quantum point contact (QPC) in Pt/NiO/Pt RS cells were formed by semiforming, the first step of the forming process. In this study, we examine correlation between microscopic structures in NiO layers and forming characteristics in the Pt/NiO/Pt cells. The appearance condition of the quantized conductance is considered to be associated with the composition ratio of O to Ni of either equivalent to or larger than a critical value. Furthermore, we proposed a RS model based on the forming characteristics especially obtained from the RS cells with different size. Defects which act as the source of a conductive filament including a QPC by semiforming may be randomly distributed in a NiO layer according to Poisson statistics.