Interaction between untreated SrTiO3 substrates and solution-derived YBa2Cu3O7-δ films

In this work it is shown how SrTiO3 substrates interact with YBa2Cu3O7-δ thin films during film processing. The effect of this interdiffusion on morphology and transport properties is analyzed. The films were deposited by low fluorine Metal Organic Decomposition (MOD) on SrTiO3 (0 0 1) single crystals. In general, a sharp c-axis oriented growth and high critical temperature (Tc) were observed in all samples; however, the surface of the otherwise good-quality films is spoiled by the presence of inhomogeneous circular areas of seemingly different appearance and texture. In order to understand the nature of these defects, the substrates and the films were deeply investigated by optical microscopy, scanning and transmission electron microscopy (SEM, TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), contact-stylus surface profilometry (SSP), Atomic Force Microscopy (AFM) and time of flight secondary ion mass spectrometry (ToF-SIMS). The round spots are the manifestation, on the film surface, of ion interdiffusion from the substrate into the YBCO film Spot-free samples can be obtained with different pre-treatments of the SrTiO3 substrates. Although these defects are detrimental for the film local structure, Jc values are not significantly affected, although the defects' influence might become substantial while working on smaller scales.