ION-BEAM CONTROLLABLE MODIFICATION OF YBA2CU3O7-X SUPERCONDUCTING THIN-FILMS

The superconducting transport properties of high-quality epitaxial YBa2Cu3O7-x thin films have been controllably modified using Ar+ ion implantation. It was found that both the critical current density J(c) and the superconducting transition temperature T(c) significantly decreased with fluence. However, when J(c) (at 77 K, H = 0) decreased by six orders of magnitude, T(c) only decreased from 89 to 77.5 K. A fluence of 5 X 10(12) Ar/cm2 was sufficient to reduce J(c) near zero, but T(c) still remained above 77 K. We have observed the structure and the morphology of the sample using x-ray diffraction and high-resolution transmission electron microscopy. A film irradiated with Ar+ ions became semiconductor at a bombardment fluence of about 1.2 X 10(13) Ar/cm2, while its superconducting state completely disappeared for an Ar+ dose of about 2.2 X 10(13) Ar/cm2. An Ar+ fluence of 5 X 10(14) Ar/cm2 made the sample amorphous with so high resistivity that it could be treated as insulator. The experimental results showed the possibility of fabricating Josephson junction devices from YBa2Cu3O7-x superconducting thin films and patterning this kind of films by ion implantation technique.