Development of Cryogenic X-Ray Detectors Based on Mo/Au TES

Transition edge sensors (TESs) have emerged as highly sensitive radiation detectors with applications ranging from astrophysics to materials science. In the framework of the Athena X-ray space telescope, we have developed Mo/Au-based TES devices designed to meet the ESA specifications for the X-IFU instrument. The detectors were fabricated using a Mo/Au/Au trilayer process and characterized in a dilution refrigerator using a SQUID readout. From I to V curves and complex impedance measurements, we extracted the electrothermal parameters of the TES, which are consistent with theoretical models. Noise spectra were analyzed to estimate the energy resolution, and an excess noise factor was obtained from the comparison of theoretical and experimental data. A spectral resolution below 4 eV was achieved for 5.9 keV X-rays from a ⁵⁵ Fe source.