Universal understanding of direct current transport properties of ReRAM based on a parallel resistance model

We propose a parallel resistance model (PRM) in which total resistance (R_total) is given by the parallel connection of resistance of a filament (R_fila) and that of a film excluding the filament (R_excl)—that is, 1/R_total = 1/R_fila + 1/R_excl—to understand direct current (dc) electric properties of resistive random-access memory (ReRAM). To prove the validity of this model, the dependence of the resistance on temperature, R(T), and the relative standard deviation (RSD) of R_HRS of Pt/NiO/Pt on the area of a top electrode, S, are investigated. It is clarified that both the R(T) and RSD depended on S, and all such dependencies can be explained by the PRM. The fact that R_total is decided by the magnitude relation between R_fila and R_excl makes transport properties S-dependent and hinders the correct understanding of ReRAM. Smaller S is essential to observe the intrinsic transport properties of ReRAM filaments.