Effect of laser irradiation on the structure and properties of dielectric column clusters in the YBaCuO superconducting films

The effect of laser irradiation on the structure and properties of the YBa$_2$Cu$_3$O$_{7-\delta}$ epitaxial super-conducting films ($T_c$ = 90–91 K) that are grown on the SrTiO$_3$ and LaAlO$_3$ substrates is studied. The films exhibit a system of pyramidal peaks that are incorporated in the single-crystal structure of the film whose system of the $(00l)$ planes is parallel to the surface of the substrate. It is demonstrated that the peaks represent growth defects that result from the relaxation of the accumulating strain due to the mismatch of the crystallographic parameters of the growing layers of the film and substrate. The island structures that are formed owing to the relaxation of strains acquire the $(11l)$ or $(10l)$ orientation and penetrate through the film layers in the course of growth. It is demonstrated that the irradiation using relatively short laser pulses makes it possible to modify the structure of the dielectric clusters and allows the smoothing of the film surface at an insignificant (5–10%) decrease in the concentration of the superconducting phase. An increase in the energy density to a level of greater than 100 mJ/cm$^2$ when the number of pulses is greater than five causes an increase in the volume of dielectric phases and the worsening of parameters.