Synthesis and characterization of superconducting FeSe nanowires

Highlights: • FeSe nanowires were synthesized by surface-assisted vapor-solid reaction. • The nanowires show superconductivity below 9.2 K (T_c0). • The suitable growing conditions of the nanowires were discussed. Iron selenide (FeSe) nanowires have been synthesized on the large-scale by a facile surface-assisted vapor-solid reaction. The typical nanowires prepared with Fe foil/Se molar ratio of 1: 0.1 at 550 °C for 12 h have a width of ∼32 nm, a thickness of ∼5 nm, and a length up to 30 μm. The nanowires are indexed as β-FeSe (tetragonal) with trace amounts of α-FeSe (hexagonal) by X-ray diffraction (XRD). High resolution transmission electron microscope of a single nanowire shows intergrowth between β- and α-FeSe. The electric transportation measurements shows that the nanowires are superconductors of T_c0 = 9.2 K (critical temperature of zero resistance). Suitable growth conditions of the nanowires are discussed.