Conductance tomography of conductive filaments in intrinsic silicon-rich silica RRAM† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr04982b Click here for additional data file.

Fig. S1. Enlarged version of Fig. 1, the structure and electrical characteristics of our devices. (a) Device schematic showing our individually patterned TiN/SiOx/TiN devices on a SiO2/p-­‐Si substrate. (b) Typical switching characteristics for our metal-­‐insulator-­‐ metal devices. Following an electroforming sweep (1), the device may be reset (2) and set (3) repeatedly to cycle between 'on' and 'off' states. The state of the device may be read by applying a small bias, usually 0.5 V. At this voltage the resistance contrast between the 'on' and 'off' states is around three orders of magnitude. Fig. S2. Typical surface distortions observed as a result of landing a tungsten needle on pristine SiO x and applying a voltage bias. (a) AFM tomography of the biased region, showing a small surface distortion. (b) Correlation of CAFM conductivity with the surface distortion in (a). This feature corresponds to the filament shown in Figs. 5 and S5. 0 1 2 3 4 5