Characterization of a Mo/Au Thermometer for ATHENA

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
$(T_{C})$
down to 100 mK, are deposited by sputtering at room temperature
$(RT)$
on
$\hbox{Si}_{3}\hbox{N}_{4}$
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
$(\alpha \approx 600)$
. Results show a good coupling between Mo and Au layers and excellent
$T_{C}$
reproducibility, allowing to accurately correlate
$d_{Mo}$
and
$T_{C}$
. Since
$d_{Au}$
is bigger than
$\xi_{M}$
for all analyzed samples, bilayer residual resistance can be modified without affecting
$T_{C}$
. Finally, first current to voltage measurements at different temperatures are measured and analyzed, obtaining the corresponding characterization parameters