Critical ReRAM Stack Parameters Controlling Complimentary versus Bipolar Resistive Switching

The thickness of the oxygen scavenging metal layer, forming the Ohmic contact in HfOx and TaOx VCM-type Metal-Oxide ReRAM cells, was found to be the critical experimental parameter controlling stable bipolar resistive switching versus the occurrence of single-cell complimentary switching. It is argued that the physically controlling parameter is the effective work function (a)symmetry between top and bottom electrode contact of the ReRAM cell. For a thin metal cap layer, oxidation increases the effective work function changing from Ohmic to a more blocking contact behavior.