Linear correlation between the c-axis lattice constant and superconducting critical temperature in FeSe0.5Te0.5 thin films

Abstract

Using x-ray diffraction, scanning electron microscopy, transmission electron microscopy, and electrical resistance analyses, we investigate structural and superconducting properties of FeSe _0.5 Te _0.5 films deposited by pulsed laser deposition on TiO _2 -buffered (CeO _2 -buffered) SrTiO _3 substrates with the buffer film thickness varying from 0 to several tens of nanometers. It is found that the SrTiO _3 /TiO _2 (or CeO _2 )/FeSe _0.5 Te _0.5 film in a proper thickness range of the buffer film shows a higher superconducting transition temperature ( T _c ) than the SrTiO _3 /FeSe _0.5 Te _0.5 film without buffer layer, indicating that the buffer layer can enhance T _c . Both T _c and the c -axis lattice constant of FeSe _0.5 Te _0.5 films increase first and then decrease with the buffer film thickness, each exhibiting its maximum at a particular buffer film thickness, and both of them show an almost linear correlation.

Keywords

• pulsed laser deposition
• FeSe0.5Te0.5
• films
• buffer layers
• superconductivity