[en] We report the low-temperature study of very thin Nb_xSi_1-x films that are used in various systems for astrophysical detection with bolometers. We have decreased the thin film thicknesses from 60nm down to 12.5nm 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

[en] Random coincidences of events could be one of the main sources of background in the search for neutrino-less double-beta decay of ${}^{100}$Mo with macro-bolometers, due to their modest time resolution. Scintillating bolometers as those based on Li${}_2$MoO${}_4$ crystals and employed in the CROSS and CUPID experiments can eventually exploit the coincident fast signal detected in a light detector to reduce this background. However, the scintillation provides a modest signal-to-noise ratio, making difficult a pile-up pulse-shape recognition and rejection at timescales shorter than a few ms. Neganov-Trofimov-Luke assisted light detectors (NTL-LDs) offer the possibility to effectively increase the signal-to-noise ratio, preserving a fast time-response, and enhance the capability of pile-up rejection via pulse shape analysis. In this article we present: (a) an experimental work performed with a Li${}_2$MoO${}_4$ scintillating bolometer, studied in the framework of the CROSS experiment, and utilizing a NTL-LD; (b) a simulation method to reproduce, synthetically, randomly coincident two-neutrino double-beta decay events; (c) a new analysis method based on a pulse-shape discrimination algorithm capable of providing high pile-up rejection efficiencies. We finally show how the NTL-LDs offer a balanced solution between performance and complexity to reach background index ∼10${}^{-<!--\; ???\; -->4}$ counts/keV/kg/year with 280 g Li${}_2$MoO${}_4$ (${}^{100}$Mo enriched) bolometers at 3034 keV, the Q${}_{\mathrm{\beta <!--\; ??\; -->}\mathrm{\beta <!--\; ??\; -->}}$ of the double-beta decay, and target the goal of a next generation experiment like CUPID.