Resistive Switching\nCharacteristics of NiO Thin Films\nInfluenced by Changes in the Diameter of Nanometer-Scale Top Electrodes

We investigated the forming, set, and reset voltages\naffected by\nthe area of the top electrodes of a resistive random access memory\n(RRAM) capacitor fabricated by epitaxial NiO thin films. NiO RRAM\ncapacitors with Au top electrode with a diameter of 100 μm showed\ntypical unipolar switching characteristics. Au top electrodes with\ndiameters of 10, 20, and 30 nm were formed on the surface of epitaxial\nNiO thin films by e-beam lithography. The forming, set, and reset\nvoltages tended to decrease as the diameter of NiO RRAM capacitors\nwith nanosized Au top electrodes decreased. As the area of the Au\ntop electrodes increases, the volume of space in which the conductive\nfilaments formed within the NiO RRAM capacitors can be formed becomes\nlarger. This causes the conductive filament to be formed at relatively\nlow energy, giving low forming voltages, while increasing the diversity\nof paths, causing a wide forming voltage distribution.