Fabrication and characterization of AlMn alloy superconducting films for 0vbb experiments

Abstract: Neutrinoless double-beta decay (0vbb) experiments constitute a pivotal probe for elucidating the characteristics of neutrinos and further discovering new physics. Compared to the neutron transmutation doped germanium thermistors (NTD-Ge) used in 0vbb experiments such as CUORE, transition edge sensors (TES) theoretically have a relatively faster response time and higher energy resolution. These make TES detectors good choice for next generation 0vbb experiments. In this paper, AlMn alloy superconducting films, the main components of TES, were prepared and studied. The relationship between critical temperature (Tc) and annealing temperature was established, and the impact of magnetic field on Tc was tested. The experimental results demonstrate that the Tc of AlMn film can be tuned in the required range of 10 - 20 mK by using the above methods, which is a key step for the application of AlMn TES in 0vbb experiment. In the test range, the Tc of AlMn film is sensitive to out-of-plane magnetic field but not to the in-plane magnetic field. Furthermore, we find that a higher annealing temperature results in a more uniform distribution of Mn ions in depth, which opens a new avenue for elucidating the underlying mechanism for tuning Tc.