Fig. 4: Structural measurements during electrical switching.

a Voltage-current curves measured in a VO₂/TiO₂ device at room temperature. Adapted from ref. ⁷⁸. b Dark-field TEM images (left) and selected area diffraction patterns (right) of the VO₂/TiO₂ device in a), measured at different values of the applied bias voltage: 0 V (top) and 1 V (bottom). Application of the above threshold bias leads to the structural transition from the monoclinic phase (M1) to the rutile one (R). The coloured arrows indicate the base vector of different monoclinic domains. Adapted from ref. ⁷⁸. c Current-voltage curve measured on a ~1 mm × ~1 mm × ~200 μm Ca₂RuO₄ single crystal sample, along with optical micrographs showing the expansion of the metallic phase (labelled L). Adapted from ref. ⁸¹. d Left panel: X-ray diffraction patterns showing the (006) reflections at different amplitudes of the electric field applied to a single crystal Ca₂RuO₄ sample. Top right panel: volume fraction of the insulting structure (S-Pbca) and metallic structure (L-Pbca) as a function of the applied electric field. Bottom right panel: current-electric field curve measured simultaneously with the X-ray diffraction. Adapted from ref. ⁸⁰.