ION-IMPLANTATION AND MASS-TRANSPORT IN YBA2CU3O7-DELTA FILMS AND SUBSTRATES

This review discusses our previous work, covering the topic of keV-MeV ion implantation into YBa2Cu3O7-delta (YBCO) thin film/substrate comb inations and bulk oxide samples. This includes 50 keV H-2(+) implantat ion (10(12)/cm(2) and 10(16)/cm(2)), 200 keV O+ implantation (10(12) O -16/cm(2), 5 x 10(14) O-18/cm(2) and 5 x 10(16) O-18/cm(2)), 200 keV N e-20(+) implantation (5 x 10(14)/cm(2)), and 1.5 MeV Au-197(+) implant ation (5 x 10(15)/cm(2))at room temperature. The experimental results show that the electrical properties of YBCO films are very sensitive t o irradiation damage. Implantation at very low dose (i.e. a damage lev el up to 4.2 x 10(-4) dpa) can result in an increase of the critical c urrent, J(c), at lower temperatures. a damage level of about 0.06 dpa destroys the superconductivity in YBCO films, whereas a damage level o f about 0.18 dpa renders a film amorphous. SIMS depth profiling was us ed to check the range data of the ion implantation and to obtain the d iffusion coefficients of H, O, and Au in the YBCO films. The implanted O-18 starts to migrate into the deeper undamaged layers of a YBCO fil m at a temperature between 250 degrees C and 300 degrees C. The appare nt diffusion coefficient of oxygen, in the c-direction of a c-axis ori ented film, is located between the c-axis value and the a-b plane valu e for a bulk single crystal. Short-circuit diffusion is thought to pla y an important role in determining this high mobility of oxygen. The i on implantation is shown to be a valuable method for determining the d iffusion coefficient in YBCO thin films. Our studies have shown that t he diffusion coefficients of implanted species follows the order H > O > Au. (C) 1998 Elsevier Science B.V.