Development of Mo/Au transition edge sensors for cryogenic x-ray detectors

Póster presentado al Encuentro RIA-SpaceTec: Nuevas perspectivas en el desarrollo de instrumentación astronómica en España, organizadas por la red SpaceTec-CM (Desarrollo de nuevas tecnologías para instrumentación espacial en la Comunidad de Madrid: S2013/ICE-2822 con el apoyo y la financiación de la Red de Infraestructuras en Astronomía (RIA-MINECO). Las jornadas se celebraron del 10 al 12 de febrero de 2016, en la Sede Central del CSIC (Serrano 117, Madrid).The so-called Transition Edge Sensors (TES) , whose basic element is a superconducting film operating at cryogenic temperatures (~100mK), constitute high performance detectors for a very wide radiation range. Thus, they are considered essential for extremely sensitive astronomic instruments, either on ground or in space, such as EDELWEISS, CRESST, BICEP2, SCUBA2, ACTPol, SAFARI and ATHENA’s X-IFU, as well as for other applications in science and industry. TES X-ray detectors with extremely high spectral resolution have been fabricated by NASA and SRON, using respectively Mo/Au or Ti/Au bilayers as the sensing element and Bi or Au as absorber. We report here our progress in the fabrication of TES X-ray detectors based on Mo/Au bilayers, within the framework of the initiative to develop a european backup for the X-IFU detector. Mo/Au TES are fabricated on SiN membranes in Ultra High Vacuum conditions through a two-step deposition process, using sputtering and electron-beam deposition, followed by dry etching photolithography. Superconducting Nb wiring is used. Electrodeposited Bi is being developed as absorber. An advanced specific characterization setup has been implemented, involving complex impedance and I-V curve measurements using superconducting electronics in a dilution refrigerator (base temperature