Transition-edge sensors using Mo/Au/Au tri-layer films

The proximity effect to reduce the transition temperature of a superconducting film is frequently used in transition-edge sensors. Here, we develop these transition-edge sensors using Mo/Au/Au tri-layer films to detect soft x-rays. They are equipped with an overhanging photon absorber. We reduce the fabrication complexity by integrating the sensor patterning with the tri-layer film formation. We determine the electro-thermal parameters of the sensors through a series of resistance vs. temperature and current vs. voltage measurements. We also demonstrate their energy-resolving capability by using a 55 Fe radioactive x-ray source. The best energy resolution was approximately 6.66 eV at 5.9 keV, with a theoretical count rate of 500 Hz.