1. A non-volatile memory device, comprising: a first electrode; a resistive switching material stack overlying the first electrode, the resistive switching material stack comprising a first resistive switching material and a second resistive switching material, wherein the first resistive switching material overlies the first electrode, wherein the first resistive switching material overlying the second resistive switching material, the first resistive switching material being characterized by a first switching voltage, the first switching voltage being characterized at least by a first amplitude, the second resistive switching material being characterized by a second switching voltage, the second switching voltage being characterized at least by a second amplitude, wherein a second amplitude is no greater than the first amplitude; and a second electrode comprising at least a metal material overlying the first resistive switching material, the metal material being physically and electrically in contact with the first resistive switching material.