Epitaxial rhenium thin films for superconducting quantum circuits

Orateur : Cécile NAUD (Institut NEEL)

This work has been performed in the frame of the realization of superconducting quantum circuits. Up to now, most of the superconducting circuits have bee n realized using aluminium. These films are polycrystalline. High density of crystal defects induces scattering processes for the charge carriers and limits the coherence time of the circuits. This is the reason why we are preparing our rhenium superconducting thin films by molecular beam epitaxy in collaboration with B. Gilles from the SIMAP laboratory. The rhenium has been chosen because the lattice mismatch between rhenium and sapphire [0001] is small (about -0.47% at room temperature in the in-plane direction <01-10>). The quality of the layer as well as the interface between sapphire and rhenium is very high. Moreover, rhenium does not oxidise, leading to clean interfaces. This talk will present the growth of epitaxial rhenium films and the fabrication of micro and nano-circuits from these films. Finally transport measurement will be discussed. In particular I will present the low temperature characterization of very narrow wires and the properties of microwave quarter wavelength resonators based on superconducting rhenium.

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