Abstract
The discovery of iron-based superconductors paved the way for advanced possible applications, mostly in high magnetic fields, but also in electronics. Among superconductive devices, nanowire detectors have raised a large interest in recent years, due to their ability to detect a single photon in the visible and infrared (IR) spectral region. Although not yet optimal for single-photon detection, iron-based superconducting nanowire detectors would bring clear advantages due to their high operating temperature, also possibly profiting of other peculiar material properties. However, there are several challenges yet to be overcome, regarding mainly: fabrication of ultra-thin films, appropriate passivation techniques, optimization of nano-patterning, and high-quality electrical contacts. Test nanowire structures, made by ultra-thin films of Co-doped BaFe2As2, have been fabricated and characterized in their transport and intrinsic noise properties. The results on the realized nanostructures show good properties in terms of material resistivity and critical current. Details on the fabrication and low temperature characterization of the realized nanodevices are presented, together with a study of possible degradation phenomena induced by ageing effects.
Highlights
Most widespread applications of superconducting nanowires regard their use as single-photon detectors, due to their ability in detecting single photons in the visible and IR spectral region [1,2]
The interest in superconducting nanowires has recently increased, due to their possible application in quantum technologies, including quantum sensing and computing. This has been highlighted in the case of YBa2Cu3O7-x (YBCO) nanowires with phase-slip dynamics, where evidence of energy-level quantization in the nanowires has been reported [7]
It has been shown that the absorption of a single photon changes the quantum state of the nanowire, an important result for the development of single-photon detectors with high operating temperature and superior temporal resolution [7]
Summary
Most widespread applications of superconducting nanowires regard their use as single-photon detectors, due to their ability in detecting single photons in the visible and IR spectral region [1,2]. Traditional superconducting nanowire single-photon detectors (SNSPDs) have the advantage of offering single-photon sensitivity, combined with low dark count rates [8], low jitter [9], short recovery times, and free-running operation [2], one drawback is their low operating temperature This is essentially due to the fact that current SNSPDs are fabricated using mostly conventional low-temperature superconductors, such as NbN and WSi [10,11], in order to achieve high sensitivity and to simplify nanofabrication processes. The recently discovered iron-based superconductors have attracted great interest to explore their potentialities in the field of large-scale current transport [16,17] and in microelectronics or nanoelectronics applications [18,19] These compounds could pave a new way to the fabrication of superconducting nanowires, profiting of intrinsic material properties to improve detection performances (in particular, speed and efficiency). There are several issues to be taken into account that are mainly related to the occurrence of non-hysteretic current-voltage characteristics (no switching), to the difficulty in fabricating ultra-thin films (dead layer problem of high-Tc compounds), and to the easy surface degradation
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