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Development of a transition-edge sensor bilayer process providing new modalities for critical temperature control



Joel Weber, Kelsey Morgan, Daikang Yan, Christine Pappas, Abigail Wessels, Galen O'Neil, Douglas Bennett, Gene C. Hilton, Daniel Swetz, Joel Ullom, Dan Schmidt


Transition-edge sensors (TESs) are thermal detectors in which a superconducting film that is electrically biased in the superconducting-to-normal transition is used as a thermometer. In most TESs, the film is a superconductor-normal metal bilayer where the two materials and their thicknesses are chosen to achieve various specifications including the transition temperature Tc. Traditionally, the materials in the bilayer are deposited in sequence without breaking vacuum in order to achieve a clean, uniform bilayer interface at the wafer-scale. This approach leads to constraints in material properties, fabrication techniques and, ultimately, TES designs. To overcome these constraints, we have developed a bilayer fabrication process that allows the layers to be deposited and patterned separately with an exposure to atmosphere between the deposition steps. We demonstrate better than 6% transition-temperature uniformity across a 7.6 cm (3 in) substrate and present satisfactory spectra from TES x-ray detectors fabricated in this fashion. We show how the new hybrid additive-subtractive TES fabrication process creates new design possibilities, including broad tuning of Tc across a substrate with a single bilayer thickness.
Superconductor Science and Technology


superconducting transition-edge sensors, x-ray detectors, microfabrication


Weber, J. , Morgan, K. , Yan, D. , Pappas, C. , Wessels, A. , O'Neil, G. , Bennett, D. , Hilton, G. , Swetz, D. , Ullom, J. and Schmidt, D. (2020), Development of a transition-edge sensor bilayer process providing new modalities for critical temperature control, Superconductor Science and Technology, [online], (Accessed May 29, 2024)


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Created September 21, 2020, Updated January 30, 2023