Characterization of NbSi films for TES bolometers

摘要

Future space experiments will require large arrays of sensitive detectors in the submillimeter and millimeter range.Superconducting transition-edge sensors (TESs) are currently under heavy development to be used as ultra sensitivebolometers. In addition to good performance, the choice of material depends on long term stability (both physical andchemical) along with a good reproducibility and uniformity in fabrication. For this purpose we are investigating theproperties of co-evaporated NbSi thin films. NbSi is a well-known alloy for use in resistive thermometers. We present afull low temperature characterization of superconductive NbSi films. In order to tune the critical temperature of the NbSithermometers down to the desired range, we have to adjust the concentration of niobium in the NbSi alloy. Tests aremade using 4He-cooled cryostats, 300mK 3He mini-fridges, Resistance Bridges and commercial SQUID. Measuredparameters are the critical temperature, the sharpness of the transition. Noise measurements are on-going.