PREPARATION OF A-AXIS ORIENTED YBA2CU3O7 AND PRBA2CU3-XGAXO7 THIN-FILMS

For Josephson junctions, a-axis oriented YBa2Cu3O7 films and a suitable 123-structured barrier material are desirable. We have deposited a-axis oriented films of YBa2Cu3O7 and PrBa2Cu3-xGaxO7 on SrTiO3 and LaAlO3 by dc magnetron sputtering using a two step process: Nucleation at lowered deposition temperature is followed by deposition at higher temperature which improves the electrical properties of the films. We have shown that by substituting Ga for Cu the resistivity of PrBa2Cu3O7 at 77K can be raised by several orders of magnitude. The practical range of substitution for dc sputtering was x less-than-or-equal-to 0.1. The effect of substitution has also been investigated by Raman spectroscopy which shows evidence for preferred substitution at the Cu(1)-sites.