A study of 2H trapping in YBa2Cu2O7−δ /LaAlO3 〈100〉 samples under 2H+ irradiation

Abstract

A c-axis oriented YBa2Cu3O7−δ film, 180–230 nm thick, deposited onto 〈100〉 LaAlO3 by dc sputtering was irradiated at room temperature with 50 keV 2H+ (deuterium) ions to a dose of 1×1016 cm−2. Secondary-ion-mass spectroscopy analysis shows that after implantation the implanted 2H is trapped in both the film and the substrate. For example, when the thickness of the YBCO film is equal to ∼180 nm, it contains about 4.5% of the retained dose. The as-implanted 2H distribution is essentially Gaussian-like and the depth (R̂p) of maximum 2H concentration is ∼485 nm. It is obvious that the target crystallinity has to be taken into account for the range data, since the experiment values (R̂p,R̄p, and ΔRp) are obviously larger than the corresponding values from the transport of ions in matter code. This implantation makes the YBa2Cu3O7−δ film more granular. Within the irradiated LaAlO3 substrate, a damaged band was observed by cross-sectional transmission electron microscopy, which was centered at about 85% of R̂p(exp).

Critical temperature depth profiling and improvement of YBa2Cu3O7 weak links produced by ion modification

“…Moreover, x-ray and crosssection transmission electron microscopy results 15 deuterium irradiated films support our conclusion, that the modification makes the YBa 2 Cu 3 O 7 film more granular, maintaining the mainly epitaxial crystalline structure of the film unchanged. It should be noted that our films showed such granular properties inside the film, in contrast to experiments, 14,15 where the ion energies were very high and the whole thickness of the films was irradiated homogeneously. A possible inhomogeneous etching around the created defects can not be ruled out, but this can be also a result of the modification, because it is observed only in the modified part of the film.…”

“…This observation can be explained by nonhomogeneous properties of the irradiated film, which becomes ''granular'' after the modification. Similar behavior was found in Ne and 2 H ions irradiated YBa 2 Cu 3 O 7 thin films, 14,15 resembling granular Pb and Sn superconducting thin films, 16 where grains of good superconductor are decoupled in a film. Moreover, x-ray and crosssection transmission electron microscopy results 15 deuterium irradiated films support our conclusion, that the modification makes the YBa 2 Cu 3 O 7 film more granular, maintaining the mainly epitaxial crystalline structure of the film unchanged.…”

“…Similar behavior was found in Ne and 2 H ions irradiated YBa 2 Cu 3 O 7 thin films, 14,15 resembling granular Pb and Sn superconducting thin films, 16 where grains of good superconductor are decoupled in a film. Moreover, x-ray and crosssection transmission electron microscopy results 15 deuterium irradiated films support our conclusion, that the modification makes the YBa 2 Cu 3 O 7 film more granular, maintaining the mainly epitaxial crystalline structure of the film unchanged. It should be noted that our films showed such granular properties inside the film, in contrast to experiments, 14,15 where the ion energies were very high and the whole thickness of the films was irradiated homogeneously.…”