Role of Oxygen Defects in Conductive-Filament Formation in Y 2 O 3 -Based Analog RRAM Devices as Revealed by Fluctuation Spectroscopy

Low-frequency noise in Y2O3-based resistive random-access memory devices with analog switching is studied at intermediate resistive states and as a function of dc cycling. A universal 1/f(alpha)-type behavior is found, with a frequency exponent of alpha approximate to 1.2 that is independent of the applied reset voltage or the device resistance and is attributed to the intrinsic abundance of oxygen vacancies unique to the structure of yttria. Remarkably, the noise magnitude in the high resistive state systematically decreases through dc training. This effect is attributed to the stabilization of the conductive filament via the consumption of oxygen vacancies, thus reducing the number of active fluctuators in the vicinity of the filament.