Preparation of thin films of Y1Ba2Cu3 O7-x by magnetron sputtering techniques

Three variations of sputtering for growing thin films of Y₁ Ba₂Cu₃O_7-x are examined: a three-metal cosputtering technique requiring a postanneal at high temperatures, an in situ process using a inverted cylindrical magnetron sputter gun, and another in situ process using an planar target in an off-axis geometry. The films are grown primarily on a magnesium oxide substrate because it is readily available, inexpensive, and its low dielectric constant permits convenient microwave circuit design. It is found that the cosputter process with postanneal produces films with depressed T_c´s and J_c´s. The inverted cylindrical magnetron sputtering has yielded the best films, showing complete transitions as high as 87 K and J_c=4×10⁶ A/cm² at 4 K. The off-axis results are not quite as good, with 79 K complete transitions. By lowering the substrates further out of the plasma in the off-axis system, films can be improved by avoiding damage from negative ions