Nanoscale Investigation of New Fe-Based Superconductors.

摘要

The researchers have successfully synthesized high quality beta-FeSe- type iron chalcogenide nanowires (NWs) from annealing thin films prepared by pulse laser deposition method. Three kinds of NWs with nominal composition (FeSe0.9, FeSe0.3Te0.7 and FeTe0.8S0.2) have been prepared and carefully characterized by transmission electron microscope (TEM). Most analyzed NWs reveal good tetragonal structure along the (100) crystal direction. The energy dispersive spectroscopy studies and high resolution TEM (HRTEM) image demonstrate good compositional uniformity, except a thin layer of oxide on the surface. The FeSe0.9 NWs don't show superconductivity because they are highly Se rich. The other two types of NWs show a high and sharp superconducting transition. In addition, a transition tail is observed in the NWs with size smaller than 100nm, which might be due to the thermally activated phase slip effect.