Devices for Thermal Conductivity Measurements of Electroplated Bi for X-ray TES Absorbers

Electroplated bismuth (Bi) is commonly used in transition-edge sensors (TESs) for X-rays because of its high stopping power and low heat capacity (Collan Phys Rev B 1:2888, 1970, Yan Appl Lett 111:192602, 2017). Bi usually grown on top another metal that acts as seed layer, typically gold (Au), making it challenging to extrapolate thermoelectric properties. In this work, we present four-wire resistance measurement structures allow us measure a function temperature electroplated independently Au. The results show the thermal conductivity at 3 K enough ensure correct thermalization X-ray photons when an absorber TESs.