We have studied the formation of nanogaps by électromigration of gold nanowires. Electromigration relies on large current densities to break a thin and narrow metallic wire and can be used for the electrical characterization of nanometer scale objects. Real time atomic force microscopy during the electromigration process has unraveled the dynamic of the process. Indeed, this study reveals that the major structural changes appear at the early stage of the process and that the final global structure of the device is directly linked to the preexisting microstructure. For the first time, we make nanogaps by electromigration of monocrystalline nanowires. We show that despite the absence of grain boundaries, it is possible to form nanogaps in epitaxial materials. The morphology of those nanogaps is more reproducible. The electrical transport properties of the polycristalline nanogaps have been measured. The obtained characteristics show particular signature that can be attributed to the presence of gold cluster formed during the electromigration process and / or to polymer from the nanowire fabrication. These results show the difficulty to measure at the molecular scale.
