Microfabricated transition-edge x-ray detectors

We are developing high performance x-ray detectors based on superconducting transition-edge sensors (TES) for application in materials analysis and astronomy. Using our recently developed fully lithographic TES fabrication process, we have made devices with an energy resolution of 4.5 +/- 0.1 eV for 5.9 keV x-rays, the best reported energy resolution for any energy dispersive detectors in this energy range. These detectors utilize micromachined thermal isolation structures and transition-edge sensors fabricated from Mo/Cu bilayers with normal-metal boundary conditions. We have found the normal-metal boundary conditions to be critical to stable and reproducible low noise operation. In this paper we present details of fabrication and performance of these devices.