Fig. 4.

Operation with a voltage source. a Temperature map of a fresh crosspoint device identical to the ones explained previously held at an applied voltage of 1 V with R _S < R _NDR). b X-ray transmission maps of a fresh crosspoint device identical to the one used in (a) that was previously subject to an applied voltage of 1 V (no bias was applied during acquisition of this data). Scale bar is 2 µm. A localized bright spot is shown in a magnified map. c X-ray absorption spectra of the “bright spot” and its “surrounding” region, color-coded to the legend. The spectral differences between the material with current and that with no current (S _i–S ₀) are also shown for the two different regions (arbitrarily offset, horizontal dashed lines indicate zero difference for respective colors)