Fabrication of superconducting MgB2 neutron detectors on Si3N4 membranes

We report a fabrication process for membrane-structured superconducting MgB₂ neutron detectors and measurement of their dc-characteristics. We prepared ¹⁰B-enriched MgB₂ thin films on Si₃N₄-film-coated Si substrates using a multiple-target sputtering system. The 170 nm thick MgB₂ thin films were processed to create meandering lines by e-beam lithography, where the line width was 1 μm and the total length reached 37.5 cm. After the front side of the device had been fabricated, it was placed into an etching apparatus to protect it. Then, the backside of the device was etched with anisotropic Si etching using ethylene diamine pyrocatechol (EDP) to increase the sensitivity of the device. The membrane-structured MgB₂ device showed superconductivity, namely, a T_C,onset of 28.2 K, a T_C,offset of 27.3 K, and an RRR of 1.18.