Lattice distortions in YBa2Cu3O7–delta thin films grown in situ by sequential ion beam sputtering

We have analyzed epitaxial, c-axis oriented YBa2Cu3O7–delta thin films grown in situ by sequential ion-beam sputtering on (100) SiTiO3 and (100) MgO substrates. X-ray diffraction studies showed the presence of both homogeneous and inhomogeneous lattice distortions along the c-direction. The c-axis lattice parameters ranged from 11.72 to 12.00 Å. The broadening of the (00l) Bragg peaks in excess of the broadening due to finite film thickness was found to be due to inhomogeneous lattice distortions. The overall trend in the data shows an increase of the inhomogeneous strains with the enlargement of the c-axis lattice parameter. The inhomogeneous lattice distortions are interpreted as fluctuations in the c-axis lattice parameter. The resistive transitions were found to be correlated to the lattice distortions. We show correlations between the midpoint Tc and the c-axis lattice parameter and between the transition widths and the inhomogeneous lattice distortions.