Coherence length in deoxygenated (103)/(013) oriented YBCO superconductor films

The coherence length ?c along c-axis direction in (103)/(013) oriented YBCO superconductor thin films has been evaluated from the temperature dependence of current–voltage (I–V) characteristics of micro-bridges in the framework of a model taking in account thermally activated magnetic flux creep in the intrinsic potential of the layered structure of the superconductor. The coherence length gradually increased from the initial value ?c=0.14nm to ?c=0.33 nm in the sample subjected to subsequent annealing steps performed in air at increasing temperatures from a range Ta=190–275°C. Structural modifications of deoxygenated samples were monitored by micro-Raman spectroscopy. The critical temperature Tc slightly increases after the initial annealing steps while a significant Tc decrease has been observed after Ta=275°C stage accompanied by appearance of the tetragonal phase in the crystal structure.