  We investigated the 1/f noise of Pt/NiO/Pt capacitors that show unipolar
resistance switching. When they were switched from the low to high resistance
states, the power spectral density of the voltage fluctuation was increased by
approximately five orders of magnitude. At 100 K, the relative resistance
fluctuation, SR/R2, in the low resistance state displayed a power law
dependence on the resistance R with exponent w = 1.6. This behavior can be
explained by percolation theory; however, at higher temperatures or near the
switching voltage, SR/R2 becomes enhanced further. This large 1/f noise can be
therefore an important problem in the development of resistance random access
memory devices.
