Abstract
In this work, the interface composition of the superconducting Ti/PdAu bilayer is tuned by an annealing process in N2 from 100 to 500 °C to control the superconducting transition temperature (Tc). This Ti-PdAu composition layer is characterized with a high-resolution transmission electron microscopy (HRTEM) and energy-dispersive spectrometer (EDS) to show the infiltration process. The surface topography, electrical, and cryogenic properties are also shown. The inter-infiltration of Ti and PdAu induced by the thermal treatments generates an intermixed layer at the interface of the bilayer film. Due to the enforced proximity effect by the annealing process, the Tc of Ti (55 nm)/PdAu (60 nm) bilayer thin films is tuned from an initial value of 243 to 111 mK which is a temperature that is suitable for the application as the function unit of a superconducting transition edge sensor.
Highlights
Superconducting transition-edge sensors (TES) [1] have been widely used in the infrared-visible region [2], and for X-ray [3] and γ-ray [4] detection with the superiority of photon-number and energy resolving capability, high quantum efficiency, and negligible dark-count rate
From the results of the high-resolution transmission electron microscopy (HRTEM), energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), surface topography, and electrical characterization, to obviously tune the Tc (>10%), the annealing temperature should be above 100 ◦ C, which is beneficial for the nanofabrication process and application of TES using Ti/PdAu films
The cross-section of the bilayer Ti/PdAu films are fabriAfter the annealing process, the cross-section of the bilayer Ti/PdAu films are fabricated by a focus ion beam milling method with a Pt layer as the protective layer
Summary
Superconducting transition-edge sensors (TES) [1] have been widely used in the infrared-visible region [2], and for X-ray [3] and γ-ray [4] detection with the superiority of photon-number and energy resolving capability, high quantum efficiency, and negligible dark-count rate. The common method to control the Tc is exploiting the proximity effect [18,19,20,21] between a superconducting and a normal metal film. Nanomaterials 2021, 11, 39 of a bilayer film composed by a superconducting film layer and a normal metal film layer is expressed as:. A PdAu alloy film, which is more stable than a pure Au film, is used as the normal metal film to tune the Tc of Ti films. From the results of the high-resolution transmission electron microscopy (HRTEM), energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), surface topography, and electrical characterization, to obviously tune the Tc (>10%), the annealing temperature should be above 100 ◦ C, which is beneficial for the nanofabrication process and application of TES using Ti/PdAu films
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