Structural and Morphological Characterization of Iridium and Ir/Au Films for Transition Edge Sensors

Superconducting Transition Edge Sensors employed in X-ray astrophysics space missions were realized and fully characterized in the Low temperature detector laboratory at UniGe. Several samples of Ir and Ir/Au bilayer films were grown by pulsed laser deposition at different deposition rate, varying thickness and resulting variability in critical temperature (Tc) was observed. In particular, we noticed two classes of films having discrete critical temperature (Tc), one at about the critical temperature of the bulk Ir and one at around 1.6 times compared to the bulk. Structural characterization was made and interesting correlation between critical temperature (Tc) and deposition conditions were found. Detailed X-Ray Diffraction investigations suggest a possible explanation of this effect with a clear correlation between microstrain value, grain size, and critical temperatures of the films. The study has been carried out to optimize the specified conditions to grow the film under which it is possible to accurately predict the critical temperature (Tc) by analyzing the X-ray diffraction patterns of Ir/Au films.