Filament Geometry Induced Bipolar, Complementary, and Unipolar Resistive Switching under the Same Set Current Compliance in Pt/SiO(x)/TiN

The decidedly unusual co-occurrence of bipolar, complementary, and unipolar resistive switching (BRS, CRS, and URS, respectively) behavior under the same high set current compliance (set-CC) is discussed on the basis of filament geometry in a Pt/SiO(x)/TiN stack. Set-CC-dependent scaling behavior with relations I(reset) ~ R(0)(–α) and V(reset) ~ R(0)(–β) differentiates BRS under low set-CC from other switching behaviors under high set-CC due to a low α and β involving a narrow filamentary path. Because such co-occurrence is observed only in the case of a high α and β involving a wide filamentary path, such a path can be classified into three different geometries according to switching behavior in detail. From the cyclic switching and a model simulation, we conclude that the reset of BRS originates from a narrower filamentary path near the top electrode than that of CRS due to the randomness of field-driven migration even under the same set-CC. Also, we conclude that URS originates from much narrower inversed conical filamentary path. Therefore, filament-geometry-dependent electric field and/or thermal effects can precisely describe the entire switching behaviors in this experiment.