MODIFICATION OF STRUCTURAL AND TRANSPORT-PROPERTIES IN EPITAXIAL YBA2CU3OX FILMS BY PULSED-LASER IRRADIATION

Pulsed (similar to 20 ns) laser effects in epitaxial YBa2Cu3Ox/SrTiO3 thin films were investigated, using RBS/channeling for compositional a nd structural characterization and 4-point technique for electrical me asurements. It was found that laser pulse melting and following quench ing lead to a transition from a single-crystalline to a polycrystallin e state in films. The formation of grain boundaries causes a room temp erature electrical resistivity increase by a factor 10-40, depending o n the initial film properties and on the irradiation conditions. Unlik e corpuscular (ions, neutrons) irradiation, the laser pulse induced st ructural damage did not lead to the disappearance of HTS, which persis ted up to the highest laser fluences used. It was found, that a therma l model can consistently describe the fluence dependence of disorder, depth of surface relief and helps, with a simple two-layer model, in u nderstanding of fluence dependence of room temperature resistivity in a relatively thick film.