Structural and electrical properties of AuPd/Mo bi-layer films for transition edge sensors

Abstract

We have tuned the transition temperature of the AuPd/Mo bi-layer in the temperature range 100-800 mK and used models derived from the Usadel theory to predict and fit the behaviour of the transition temperature. As expected, the influence of the AuPd on the transition temperature is stronger than that found by others from pure Au, but weaker than that of pure Pd. The extracted coherence length of the Cooper pairs in the metal alloy points to the greatest influence coming from the Pd part of the AuPd. X-ray measurements show the films to be textured, with the Mo(110) and AuPd(111) peaks being dominant in the out-of-plane direction. The transition width is seen to increase with the spread of the orientation of the z direction of the individual grains.