nano-gaps*

Electrically driven metal-insulator transition in vanadium dioxide (VO₂) is of interest in novel memory devices, neural computation, and high-speed electronics. Resistive switching behavior of such devices is driven by the formation of Joule heating conductive nano-filaments between the contacts in the switched state and highly depends on the confinement and morphology of the nano-gap. We applied X-ray nano-diffraction to image the structure of 800x300 nm gap made of 100 nm VO₂ film in operando conditions. High-resolution images of the several identical gaps in the switched state show tiny filaments of the metallic phase connecting the corners of the terminals. Interestingly, these filaments always appear at the same location which evidences a direct connection with the film morphology.