Absorber Materials for Transition-Edge Sensor X-ray Microcalorimeters*

Arrays of superconducting transition-edge sensors (TES) can provide high spatial and energy resolution necessary for x-ray astronomy. High quantum efficiency and uniformity of response can be achieved with a suitable absorber material, in which absorber x-ray stopping power, heat capacity, and thermal conductivity are relevant parameters. Here we compare these parameters for bismuth and gold. We find that the thermal conductivity of these materials is highly dependent upon the thin film deposition technique. Furthermore, we briefly discuss the performance of our x-ray detectors when they possess cantilevered evaporated Bi/Au, electroplated Bi/Au, and electroplated Au absorbers.