Inhomogeneities in YBa2Cu3O7 thin films with reduced thickness

Abstract

Morphology and physical properties of mono- (YBa2Cu3O7) and multilayered (YBa2Cu3O7/SmBa2Cu3O7/ YBa2Cu3O7) superconducting thin films with thickness ranging from 90nm to 28nm have been investigated. For both types of samples, the superconducting properties degraded with reduction of film thickness. Structural and electromagnetic properties were visualized through scanning electron microscopy and magneto-optical imaging, respectively, and revealed high level of inhomogeneity for thinner (<58nm) samples. However, samples with thickness above 58nm showed enhanced homogeneity, which explains better superconducting characteristics observed in these films. Results of this work demonstrate that multilayering approach performed by conventional laser ablation results in degradation of superconducting properties in films with thickness below 90nm, although has positive impact on morphology of these films, which is crucial for device fabrication process.