HTS Bolometer on Si_xN_y Membrane Preparation and Properties

摘要

A high-T_c GdBa_2Cu_3O_(7-δ) superconducting transition edge bolometer built on a 1 um thick silicon nitride membrane was fabricated and characterized. A thin monocrystalline Si layer on top of a Si_xN_y membrane (Silicon-On-Nitride SON) was used as the starting substrate. This SON structure was made by direct wafer bonding after Chemical Mechanical Polishing (CMP). Between the Si layer and the HTS film a YSZ/CeO_2 buffer layer is used. To prevent degradation the HTS film is covered by a layer of PtO_x. A thermal conductance of G = 3.3·10~(-5) W/K with a time constant of 27 ms has been achieved using a 2 * 2 mm`2 membrane. The electrical Noise Equivalent Power (HEP) at 5 Hz is 3.7·10~(-12) W/Hz~(1/2) which is very close to the theoretical phonon noise limit of 3.6·10~(12)W/Hz~1/2), indicating that the excess noise of the superconducting film is very low. This value corresponds with an electrical detectivity D~* of 2.2·10~(10) cmHz~(1/2)/W, which is unequaled by other reported HTS bolometers. Our investigations are now aimed at decreasing the NEP for 84 urn radiation by adding an absorption layer and by further reduction of G. This bolometer is intended to be used as a detector in a Fabry-Perot based satellite instrument, designed for remote sensing of atmospheric OH.