A high-Tc superconductor bolometer on a silicon nitride membrane

In this paper we describe the design, fabrication and performance of a high-T_c GdBa₂Cu₃O_7-δ superconductor bolometer positioned on a 2×2 mm², 1 μm thick silicon nitride membrane. The bolometer structure has an effective area of 0.64 mm² and was grown on a specially developed silicon-on-nitride layer. This layer was made by direct bonding of silicon nitride to silicon after chemical mechanical polishing. The operation temperature of the bolometer is 85 K. A thermal conductance G=3.3·10^-5 W/K with a time constant of 27 ms has been achieved. The electrical noise equivalent power (NEP) at 5 Hz is 3.7·10^-12 WHz^-½ which is very close to the theoretical phonon noise limit of 3.6·10^-12 WHz^-½, meaning that the excess noise of the superconducting film is very low. This bolometer is comparable to other bolometers with respect to high electrical performance. Our investigations are now aimed at decreasing the NEP for 84 μm radiation by further reduction of G and adding an absorption layer to the detector. This bolometer is intended to be used as a detector in a Fabry-Perot based satellite instrument, designed for remote sensing of atmospheric OH