Properties of thermometric NbSi thin films and application to detection in astrophysics

We report the low-temperature study of very thin Nb x Si 1 - x films that are used in various systems for astrophysical detection with bolometers. We have decreased the thin film thicknesses from 60 nm down to 12.5 nm and shown that the sensitivity gain due to lowering the heat capacity is not to the detriment of the electron–phonon coupling or to noise characteristics. On the superconducting side, we show that, at small thicknesses, the critical temperature and the normal resistance can be adjusted by tuning the thickness and the composition of the films.