Structural investigation of resistance switching in silicon-rich silica films
Redox-based resistive RAM presents a development in non-volatile data storage, despite an incomplete understanding of switching mechanisms. However, in order to optimize and standardize device behavior it is necessary to have a better understanding of physical processes governing switching. Many oxide dielectrics have been studied in relation to switching, but silicon-based devices in particular offer a high capacity for integration into existing CMOS technologies at low cost. We present analyses of silicon-rich silica films to establish the chemical and structural processes underpinning electronic resistance switching behavior. Atomic force microscopy, x-ray photoelectron spectroscopy and secondary ion mass spectroscopy are used to characterize observed resistance changes. Reduction and structural reconfiguration of the oxide is seen to be concomitant with structural distortions and the appearance of conductive regions in otherwise-insulating material. Crucially, we demonstrate for the first time the correlation between resistance switching and the emission of oxygen from an electrically stressed dielectric film. These results confirm the current model of an oxygen-based mechanism and highlight the inherent limitations imposed by gradual oxygen depletion on device lifetime.