Atomically-flat, chemically-stable, superconducting epitaxial thin film of iron-based superconductor, cobalt-doped BaFe$_2$As$_2$

摘要

Epitaxial growth of Fe-based superconductors such as Co-doped SrFe$_2$As$_2$(SrFe$_2$As$_2$:Co) was reported recently, but has still insufficientproperties for device application because they have rough surfaces and aredecomposed by reactions with water vapor in an ambient atmosphere. This letterreports that epitaxial films of Co-doped BaFe$_2$As$_2$ grown at 700 oC showthe onset superconducting transition tempearture of 20 K. The transition issharper than those observed on the SrFe$_2$As$_2$:Co films, which wouldoriginate from their improved crystallinity. These films also haveatomically-flat surfaces with steps-and-terraces structures and exhibitchemical stability against exposure to water vapor.