Realization of Precise Tuning the Superconducting Properties of Mn-Doped Al Films for Transition Edge Sensors

Abstract

Magnetic impurities in metallic superconductors are important for both fundamental and applied sciences. In this study, we focused on dilute Mn-doped aluminum (AlMn) films, which are common superconducting materials used to make transition edge sensors and other superconducting devices. We developed a multi-energy ion-implantation technique to make AlMn films. Compared with frequently used sputtering techniques, ion-implantation provides more precise control of the Mn doping concentration in the AlMn films. It enables us to fabricate reliably AlMn films with a different superconducting transition temperature (T-c) that can match a variety of application needs. We also found that the superconducting transition temperature drops with increasing film thickness for samples with the same nominal concentration of Mn dopants. The dependence of T-c on the film thickness is attributed to the increasing implantation energy. By quantitatively analyzing the curves of T-c versus the Mn doping concentration, we propose that Mn dopants act as magnetic impurities and suppression of superconductivity is counteracted by the antiferromagnetic Ruderman-Kittel-Kasuya-Yosida interaction among Mn dopants, which is influenced by the defects induced in the ion-implantation process.