Investigation of bipolar resistive switching and the time-dependent SET process in silversulfide/silver thin films and nanowire array structures

Abstract

We report on the bipolar resistive switching (RS) behaviour observed from silver sulfide/silver (Ag2S/Ag) nanowire array and thin film structures fabricated under similar conditions. By examiningthe RS parameters measured using electrical probing with a similar tungsten probeon both types of structures, we conclude that the larger SET voltage and lowerON-state conductance in the thin film structures are the result of the longerconductive filamentary paths formed during the SET process. In addition, we foundthat the metal filament can be established at a constant voltage bias which ismuch lower than the measured SET voltage for a sweeping voltage bias, as longas the constant bias/stress voltage is applied for a sufficiently long duration.This time dependency in the SET process is possibly related to the migrationand reduction of silver ions to form silver atoms at the filamentary formationsite. Experimental results also show that an applied voltage bias, either withincreasing magnitude or duration, will increase the ON-state conductance. Thisis explained by the increased cross-sectional area of the conductive filamentarypath. From the comparative investigation of the RS parameter values obtainedfrom the two different structures, it is concluded that nanostructuring of theAg2S/Ag heterostructure from a two-dimensional thin film to a one-dimensional nanowire structureresults in an improvement in the SET process parameters.