Investigation of bipolar resistive switching and the time-dependent SET process in silver sulfide/silver thin films...

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 examining the RS parameters measured using electrical probing with a similar tungsten probe on both types of structures, we conclude that the larger SET voltage and lower ON-state conductance in the thin film structures are the result of the longer conductive filamentary paths formed during the SET process. In addition, we found that the metal filament can be established at a constant voltage bias which is much lower than the measured SET voltage for a sweeping voltage bias, as long as the constant bias/stress voltage is applied for a sufficiently long duration. This time dependency in the SET process is possibly related to the migration and reduction of silver ions to form silver atoms at the filamentary formation site. Experimental results also show that an applied voltage bias, either with increasing magnitude or duration, will increase the ON-state conductance. This is explained by the increased cross-sectional area of the conductive filamentary path. From the comparative investigation of the RS parameter values obtained from the two different structures, it is concluded that nanostructuring of the Ag2S/Ag heterostructure from a two-dimensional thin film to a one-dimensional nanowire structure results in an improvement in the SET process parameters.