Transport properties of ultrathin BaFe_1.84Co_0.16As₂superconducting nanowires

Abstract

Superconducting nanowire single-photon detectors (SNSPDs) have an absolute advantage over other types of single photon detectors except the low operating temperature.Therefore, many efforts have been devoted to find high-temperature superconducting materials that are suitable for preparing SNSPDs. Copper-based and MgB2 ultra-thin superconducting nanowires have been already reported. However, the transport properties of iron-based ultra-thin superconducting nanowires have not been studied. In this work, a 10 nm thick × 200 nm wide × 30 μm long high quality superconducting nanowire was fabricated from ultrathin BaFe1.84Co0.16As2 films by a lift-off process. The precursor BaFe1.84Co0.16As2 film with a thickness of 10 nm and root-mean-square roughness of 1 nm was grown on CaF2 substrates by pulsed laser deposition. The nanowire shows a high superconducting critical temperature T zero c =20 K with a narrow transition width of ΔT=2.5 K and exhibits a high critical current density Jc of 1.8×10 7 A cm −2 at 10 K. These results of ultrathin BaFe1.84Co0.16As2nanowire will attract interest in electronic applications, including SNSPDs.

Iron-Based Superconducting Nanowires: Electric Transport and Voltage-Noise Properties

“…A critical current I c of the order of 10 µA is measured at 8 K, as shown in the inset of Figure 4a. A non-hysteretic behavior was also reported in [20] for iron-based superconductors and in [38,39] in the case of YBCO. Some hysteresis was observed for a YBCO microbridge (not a nanowire) at T = 4 K [40].…”

“…These compounds could pave a new way to the fabrication of superconducting nanowires, also profiting of intrinsic material properties to improve detection performances (in particular, speed and efficiency). In this respect some preliminary results are reported in [20]. However, 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-T c compounds), and to the easy surface degradation.…”

Co-doped BaFe2As2 Josephson junction fabricated with a focused helium ion beam

“…The Ba122:Co thin films were grown by pulsed laser deposition (PLD) utilizing a KrF excimer laser with the wavelength of 248 nm on CaF 2 single crystal substrates (5 × 5 mm 2 ), which had been demonstrated to have superior superconducting properties compared with films deposited on other substrates. [33] The targets of nominal composition BaFe 1.84 Co 0.16 As 2 Y 2 O 3 ablated in PLD were synthesized by the solid-state reaction method. The optimal fabrication conditions to obtain highquality epitaxial thin films were a 1.4 J•cm −2 laser energy density with a repetition rate of 9 Hz, a 55 mm distance between the target and the substrate, and a substrate temperature of 825 • C in a base pressure better than 10 −7 Torr.…”

Microfabrication of NdFeAs(O,F) thin films and evaluation of the transport properties

“…The Nd1111:F thin films were grown by a molecular beam epitaxy method [21][22][23][24][25]. NdF 3 , Fe, As, Fe 2 O 3 , and Ga, charged in Knudsen cells, were used as the source materials.…”

“…However, studies targeting particle detectors using iron based superconductors are still limited. A recent paper has reported on the microfabrication of Co-doped BaFe 2 As 2 films [21], but no study has been published so far that is concerned with how the microfabrication affects the characteristics of LnFeAsO based superconductors. Here, we studied the microfabrication of NdFeAs(O,F) (Nd1111:F) with two processing methods.…”