Influence of the Interface Composition to the Superconductivity of Ti/PdAu Films

In this work, the interface composition of the superconducting Ti/PdAu bilayer is tuned by an annealing process in N₂ from 100 to 500 °C to control the superconducting transition temperature (T_c). This Ti-PdAu composition layer is characterized with a high-resolution transmission electron microscopy (HRTEM) and energy-dispersive spectrometer (EDS) to show the infiltration process. The surface topography, electrical, and cryogenic properties are also shown. The inter-infiltration of Ti and PdAu induced by the thermal treatments generates an intermixed layer at the interface of the bilayer film. Due to the enforced proximity effect by the annealing process, the T_c of Ti (55 nm)/PdAu (60 nm) bilayer thin films is tuned from an initial value of 243 to 111 mK which is a temperature that is suitable for the application as the function unit of a superconducting transition edge sensor.