Lateral Inverse Proximity Effect in Ti/Au Transition Edge Sensors
Kenichiro Nagayoshi (SRON–Netherlands Institute for Space Research)
M. de Wit (SRON–Netherlands Institute for Space Research)
E. Taralli (SRON–Netherlands Institute for Space Research)
S Visser (SRON–Netherlands Institute for Space Research)
M. L. Ridder (SRON–Netherlands Institute for Space Research)
Luciano Gottardi (SRON–Netherlands Institute for Space Research)
H. Akamatsu (SRON–Netherlands Institute for Space Research)
D. Vaccaro (SRON–Netherlands Institute for Space Research)
J.R. Gao (TU Delft - ImPhys/Optics, SRON–Netherlands Institute for Space Research)
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Abstract
We report measured Tc of superconducting Ti/Au bilayer strips with a width W varying from 5 to 50 µm. The strips were fabricated based on a Ti/Au bilayer that consists of a 41-nm-thick Ti layer to which a 280-nm-thick Au layer was added. We find that the Tc drops as W decreases and the declining trend almost perfectly follows Tc/ [mK] = - 738.4 [μ m] 2/ W2+ 91.0 , where Tc(W= ∞) of 91 mK is consistent with the intrinsic Tc of the bilayer. The result is interpreted as a consequence of the lateral inverse proximity effect originated in normal-metal microstructures, namely Au overhangs that exist at the edges of the Ti/Au bilayer. The Tc shift from the intrinsic Tc should be anticipated in addition to the longitudinal proximity effect from superconducting Nb leads when one designs Ti/Au TESs.