Ion irradiation as a wafer-scale method for amorphizing superconducting thin films*

Nanoscale superconducting structures, such as nanowires, have several promising applications in quantum technology. The nanostructures can become irreproducible when the dimensions are comparable with the grain sizes of the material. One possible solution is to use amorphous materials. We demonstrate ion irradiation as a wafer-scale method for the fabrication of amorphous superconducting thin films [1]. We study the ion irradiation treatment using argon or gallium ions on single-element and compound materials. We characterize the properties of the films with transmission electron microscopy imaging and electrical transport measurements. Our results indicate that gallium and argon ions increase disorder in the thin films in qualitatively similar manner - they destroy the grain structure, increase the resistivity, and alter the superconducting transition temperature. However, our results show that argon tends to form gas pockets that can be detrimental for certain applications, whereas gallium ion irradiation allows to produce a thin, uniform, and amorphous film that is promising, e.g., for superconducting nanowire single-photon detectors.