Characteristics of FeSe₀. ₅Te₀. ₅ Films on an Amorphous Substrate

For FeSeTe films on an amorphous dielectric substrate—K-208 grade glass—the surface morphology and elemental composition were investigated. The measured root-mean-square roughness values of the film surface were 4–6 nm in a 1 1 m ^2 area and 7–10 nm in a 10 10 m ^2 area. The determined elemental composition Fe ₁. ₀₅ Se ₀. ₅ Te ₀. ₅ was found to be close to the stoichiometric ratio. Estimates were obtained for the values of the upper critical field: H₂₂^ ab (0) 68 T and H₂₂^ ab (0) 51 T for different orientations of the magnetic field relative to the crystallographic planes of the film. The corresponding value of the anisotropy of the film properties is close to 1. 3 and comparable to the results for such films on single-crystal substrates. The coherence lengths were found to be ₀₁ (0) 2. 5 nm, ₂ (0) 1. 9 nm. The critical current density was measured and found to be at the level of 2. 1 10^4 A/cm ^2 (contact method) and 2. 3 10^4 A/cm ^2 (contactless method—SQUID), in zero field at a temperature of 2 K. Estimates for the vortex activation energy U (H) and the pinning force density were obtained. Predominance of pinning on correlated defects was demonstrated.