Temperature overshoot as the cause of physical changes in resistive switching devices during electro-formation

Resistive switching devices based on transition metal oxides require formation of a conductive filament in order for the device to be able to switch. Such filaments have been proposed to form by the reduction of oxide due to the application of the electric field, but this report seeks to rebut that interpretation. Frequently reported physical changes during electro-formation include delamination of electrodes, crystallization of functional oxide, intermixing of electrode and oxide materials, and extensive loss of oxygen presumably to the ambient. Here, we show that most of these effects are not inherent to the formation and switching processes and instead are due to an experimental artifact: the discharge of parasitic capacitances in the forming circuit. Discharge of typical BNC cables can raise the temperature of the filament to between 2000 and 5000 K resulting in extensive physical changes. Discharge and associated effects mentioned above can be eliminated using an on-chip load element without affecting the ability to switch.