Characterization of a Mo/Au Thermometer for ATHENA

Abstract

The first dark characterization of a thermometer fabricated with our Mo/Au bilayers to be used as a transition edge sensor is presented. High-quality, stress-free Mo layers, whose thickness is used to tune the critical temperature (TC) down to 100 mK, are deposited by sputtering at room temperature (RT) on Si3N4 bulk and membranes, and protected from degradation with a 15-nm sputtered Au layer. An extra layer of high-quality Au is deposited by ex situ e-beam to ensure low residual resistance. The thermometer is patterned on a membrane using standard photolithographic techniques and wet etching processes, and is contacted through Mo paths, displaying a sharp superconducting transition (α ≈ 600). Results show a good coupling between Mo and Au layers and excellent TC reproducibility, allowing to accurately correlate dMo and TC. Since dAu is bigger than ξM for all analyzed samples, bilayer residual resistance can be modified without affecting TC . Finally, first current to voltage measurements at different temperatures are measured and analyzed, obtaining the corresponding characterization parameters.