Superconducting Fe1+δSe1−xTex thin films: growth, characterization and properties

Abstract

Thin films of Fe1+δSe1−xTex (δ∼0.18 and x∼0.5) have been successfully grown on (100)-oriented single-crystallineSrTiO3 andLaAlO3 substrates by pulsed laser deposition. The crystal structure was characterizedby x-ray diffraction and the superconducting properties by electrical resistivitymeasurements. X-ray diffraction analysis establishes the growth of films withc-axis orientation. Atomic force microscopy showed a smooth surface morphology for the films grownon SrTiO3 substrates. All the films are observed to be superconducting with a transition temperature,Tc of∼8–14 K,depending on the deposition conditions. The deposition parameters were optimized to obtain good qualityfilms with Tc comparable to that of the target material. The upper critical field shows a positive curvature nearTc unlike the opposite behavior observed in conventional superconductors.